From 89f45896b74069d6ed98b1a2aeb91bfbf64c4e87 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=B5=85=E5=BF=B5?= <email@sample.com>
Date: Mon, 21 Sep 2026 21:58:09 +0800
Subject: [PATCH] feat(viewer): UI-02 dark immersive photo viewer with
 thumbnail strip
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V04 (方案 §5)：PhotoLightbox 模板重构为深色沉浸布局——顶栏（关闭/位置
计数/⋯ 减少动画菜单）+ 舞台（contain 大图 + 边缘 ‹› + 粒子/互动占位层）+
缩略图条 + 底部操作栏；业务逻辑（序列导航/缩放手势/签名刷新/下载/点赞）
原样保留。

- 新增 viewer/position.ts：§5.2 位置计数真实回退（solo→照片预览；无
  total 未到末页→已加载 N 张；全部加载→i/n；不伪造总数）
- 新增 ThumbnailStrip：当前 ±3 窗口（≤7 项）、主色 2px 描边、thumb 变体、
  滚入可见（遵守减少动画）、点击选择不新增历史
- 新增 PhotoActionBar：Like（coral 心形+计数+连续点赞提示）/Share/
  Download 均分大触控；下载关闭整项移除；原图二级菜单（▾ + 长按）
- 模态可用性：body 滚动锁、焦点进入/困住/归还触发元素、Esc 先收菜单、
  菜单内左右键不抢占、dvh + 安全区、chrome 区手势/滚轮隔离
- 分享 V04 最小实现（复制当前深链，support/clipboard 从 AlbumHeader
  提取共用）；navigator.share 编排属 Task 5
- zh-CN/en 新词条；vitest 新增 23 例（位置回退/缩略图/操作栏/焦点/滚锁）

Co-Authored-By: Claude Code <noreply@anthropic.com>
---
 apps/viewer/src/__tests__/download.spec.ts    |  24 +-
 apps/viewer/src/__tests__/lightbox.spec.ts    | 181 +++-
 .../src/__tests__/photo-action-bar.spec.ts    | 117 +++
 .../src/__tests__/thumbnail-strip.spec.ts     | 115 +++
 .../src/__tests__/viewer-position.spec.ts     |  41 +
 .../viewer/src/__tests__/viewer-route.spec.ts |  14 +-
 apps/viewer/src/components/PhotoLightbox.vue  | 782 +++++++++++-------
 .../src/components/album/AlbumHeader.vue      |  26 +-
 .../src/components/viewer/PhotoActionBar.vue  | 305 +++++++
 .../src/components/viewer/ThumbnailStrip.vue  | 184 +++++
 apps/viewer/src/i18n/locales/en.ts            |  11 +
 apps/viewer/src/i18n/locales/zh-CN.ts         |  11 +
 apps/viewer/src/support/clipboard.ts          |  28 +
 apps/viewer/src/viewer/position.ts            |  37 +
 14 files changed, 1536 insertions(+), 340 deletions(-)
 create mode 100644 apps/viewer/src/__tests__/photo-action-bar.spec.ts
 create mode 100644 apps/viewer/src/__tests__/thumbnail-strip.spec.ts
 create mode 100644 apps/viewer/src/__tests__/viewer-position.spec.ts
 create mode 100644 apps/viewer/src/components/viewer/PhotoActionBar.vue
 create mode 100644 apps/viewer/src/components/viewer/ThumbnailStrip.vue
 create mode 100644 apps/viewer/src/support/clipboard.ts
 create mode 100644 apps/viewer/src/viewer/position.ts

diff --git a/apps/viewer/src/__tests__/download.spec.ts b/apps/viewer/src/__tests__/download.spec.ts
index b5e1a4b..d1ff835 100644
--- a/apps/viewer/src/__tests__/download.spec.ts
+++ b/apps/viewer/src/__tests__/download.spec.ts
@@ -187,16 +187,16 @@ describe('photo download (P4a Task 4)', () => {
     // on/off：单按钮，无 caret/菜单。
     const browseOnly = mountLightbox(makeAlbum());
     await flushPromises();
-    expect(browseOnly.find('.control.download').exists()).toBe(true);
-    expect(browseOnly.find('.control.download-caret').exists()).toBe(false);
+    expect(browseOnly.find('.download-main').exists()).toBe(true);
+    expect(browseOnly.find('.download-caret').exists()).toBe(false);
 
     // on/on：分体按钮（caret 出现，菜单默认收起）。
     const split = mountLightbox(makeAlbum({ originalDownloadEnabled: true }));
     await flushPromises();
-    expect(split.find('.control.download-caret').exists()).toBe(true);
+    expect(split.find('.download-caret').exists()).toBe(true);
     expect(split.find('.download-menu').exists()).toBe(false);
     // 主按钮 aria 展开 = false。
-    expect(split.find('.control.download-caret').attributes('aria-expanded')).toBe('false');
+    expect(split.find('.download-caret').attributes('aria-expanded')).toBe('false');
   });
 
   it('split menu offers both variants; picking original requests the original endpoint', async () => {
@@ -204,9 +204,9 @@ describe('photo download (P4a Task 4)', () => {
     const wrapper = mountLightbox(makeAlbum({ originalDownloadEnabled: true }));
     await flushPromises();
 
-    await wrapper.find('.control.download-caret').trigger('click');
+    await wrapper.find('.download-caret').trigger('click');
     const items = wrapper.findAll('.download-menu button');
-    expect(items.map((item) => item.text())).toEqual(['下载图片', '下载原图']);
+    expect(items.map((item) => item.text())).toEqual(['浏览图', '原图']);
 
     await items[1]!.trigger('click');
     await flushPromises();
@@ -224,7 +224,7 @@ describe('photo download (P4a Task 4)', () => {
     const wrapper = mountLightbox(makeAlbum());
     await flushPromises();
 
-    await wrapper.find('.control.download').trigger('click');
+    await wrapper.find('.download-main').trigger('click');
     await flushPromises();
     expect(mockedGetPhotoDownload).toHaveBeenCalledTimes(2);
     expect(mockedGetPhotoDownload).toHaveBeenCalledWith('tok-dl', 'p1', 'browse');
@@ -236,7 +236,7 @@ describe('photo download (P4a Task 4)', () => {
     const wrapper = mountLightbox(makeAlbum());
     await flushPromises();
 
-    await wrapper.find('.control.download').trigger('click');
+    await wrapper.find('.download-main').trigger('click');
     await flushPromises();
     expect(mockedGetPhotoDownload).toHaveBeenCalledTimes(1);
     expect(openSpy).toHaveBeenCalledWith('http://img.test/p1-browse.jpg', '_blank', 'noopener,noreferrer');
@@ -245,7 +245,7 @@ describe('photo download (P4a Task 4)', () => {
     // 端点失败（网络/403 等）→ 失败提示可再见（再次点击重试）。
     openSpy.mockClear();
     mockedGetPhotoDownload.mockReset().mockRejectedValue(new Error('boom'));
-    await wrapper.find('.control.download').trigger('click');
+    await wrapper.find('.download-main').trigger('click');
     await flushPromises();
     expect(wrapper.find('.download-failed[role="alert"]').text()).toContain('下载失败');
     expect(openSpy).not.toHaveBeenCalled();
@@ -259,7 +259,7 @@ describe('photo download (P4a Task 4)', () => {
     const wrapper = mountLightbox(makeAlbum());
     await flushPromises();
 
-    await wrapper.find('.control.download').trigger('click');
+    await wrapper.find('.download-main').trigger('click');
     await flushPromises();
     expect(wrapper.find('.download-failed[role="alert"]').text()).toContain('该相册未开放下载');
     expect(wrapper.find('.download-failed').text()).not.toContain('下载失败');
@@ -270,7 +270,7 @@ describe('photo download (P4a Task 4)', () => {
     const wrapper = mountLightbox(makeAlbum());
     await flushPromises();
 
-    await wrapper.find('.control.download').trigger('click');
+    await wrapper.find('.download-main').trigger('click');
     await flushPromises();
     expect(wrapper.find('.wechat-guide[role="dialog"]').exists()).toBe(true);
     expect(wrapper.find('.wechat-guide h2').text()).toBe('保存图片指引');
@@ -289,7 +289,7 @@ describe('photo download (P4a Task 4)', () => {
     const wrapper = mountLightbox(makeAlbum());
     await flushPromises();
 
-    await wrapper.find('.control.download').trigger('click');
+    await wrapper.find('.download-main').trigger('click');
     await wrapper.find('.guide-copy').trigger('click');
     await flushPromises();
     expect(writeText).toHaveBeenCalledWith(window.location.href);
diff --git a/apps/viewer/src/__tests__/lightbox.spec.ts b/apps/viewer/src/__tests__/lightbox.spec.ts
index 5b87d77..1155537 100644
--- a/apps/viewer/src/__tests__/lightbox.spec.ts
+++ b/apps/viewer/src/__tests__/lightbox.spec.ts
@@ -1,3 +1,6 @@
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
 import { flushPromises, mount, type VueWrapper } from '@vue/test-utils';
 import { defineComponent, nextTick, ref } from 'vue';
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
@@ -12,8 +15,10 @@ import { createViewerI18n, type ViewerI18n } from '../i18n';
 import PhotoLightbox from '../components/PhotoLightbox.vue';
 import { usePhotoSequence, type PhotoSequence } from '../feed/sequence';
 
-// PhotoLightbox（Task 8）组件测试：browse 渲染/导航/序列扩展、wheel 缩放与双击
-// 复位、Esc/背景/按钮关闭、指针轻扫切换、签名过期静默重取与 404 移除上报。
+// PhotoLightbox 组件测试（Task 8 业务 + UI-02 V04 深色布局）：
+// browse 渲染/导航/序列扩展、wheel 缩放与双击复位、Esc/关闭/舞台空白点击关闭、
+// 指针轻扫切换、签名过期静默重取与 404 移除上报；V04 新增：位置计数三种
+// 真实回退、缩略图条渲染与选择、更多菜单、焦点管理、body 滚动锁、安全区。
 // 深链解析与 URL 同步在 viewer-route.spec（真实路由）覆盖。
 
 vi.mock('../api/client', async (importOriginal) => {
@@ -44,8 +49,9 @@ let i18n: ViewerI18n;
 const mounted: VueWrapper[] = [];
 
 /** 宿主：sequence + v-model photoId（镜像 ActivityPage 组装）。页面数据经
- * mockedGetPublicPhotos 的当前 mock 队列供给（与真实时序一致：挂载后到达）。 */
-function mountLightbox(photoId: string): VueWrapper {
+ * mockedGetPublicPhotos 的当前 mock 队列供给（与真实时序一致：挂载后到达）。
+ * solo：深链兜底条目（ensureInSequence 追加在序列尾部，自然位置未知）。 */
+function mountLightbox(photoId: string, options: { solo?: PublicPhoto } = {}): VueWrapper {
   const Host = defineComponent({
     components: { PhotoLightbox },
     setup() {
@@ -54,6 +60,7 @@ function mountLightbox(photoId: string): VueWrapper {
         locale: ref('zh-CN'),
         category: ref(null),
       });
+      if (options.solo !== undefined) sequence.ensureInSequence(options.solo);
       const current = ref(photoId);
       return { sequence, photoId: current };
     },
@@ -95,7 +102,7 @@ function keydown(key: string): void {
 
 /** test-utils 的 trigger 无法写 MouseEvent 只读坐标：直接派生 WheelEvent。 */
 function wheel(wrapper: VueWrapper, deltaY: number, clientX = 100, clientY = 80): void {
-  wrapper.find('.lightbox').element.dispatchEvent(
+  wrapper.find('.photo-viewer').element.dispatchEvent(
     new WheelEvent('wheel', { bubbles: true, cancelable: true, deltaY, clientX, clientY }),
   );
 }
@@ -115,7 +122,7 @@ describe('photo lightbox (Task 8)', () => {
     vi.restoreAllMocks();
   });
 
-  it('renders the current browse url with counter and like count', async () => {
+  it('renders the current browse url with position indicator and like count', async () => {
     mockedGetPublicPhotos.mockResolvedValue(
       makeList([makePhoto('p1'), makePhoto('p2', 7), makePhoto('p3')]),
     );
@@ -123,8 +130,11 @@ describe('photo lightbox (Task 8)', () => {
     await flushPromises();
 
     expect(img(wrapper).attributes('src')).toBe('http://img.test/p2-browse.jpg?s=1');
-    expect(wrapper.find('.counter').text()).toBe('2 / 3');
-    expect(wrapper.find('.likes').text()).toBe('7 次点赞');
+    // 3 张全部加载完成（无更多页）→ 筛选序列 i / n（§5.2）。
+    expect(wrapper.find('.position-indicator').text()).toBe('2 / 3');
+    // 底部操作栏（V04）：Like 计数 + Like/Share 标签（无下载控制器 → 下载位省略）。
+    expect(wrapper.find('.like-count').text()).toBe('7');
+    expect(wrapper.findAll('.action-label').map((label) => label.text())).toEqual(['点赞', '分享']);
   });
 
   it('navigates with buttons and arrow keys, keeping the list order', async () => {
@@ -150,17 +160,18 @@ describe('photo lightbox (Task 8)', () => {
     expect(wrapper.find('.nav.next').attributes('disabled')).toBeUndefined();
   });
 
-  it('closes on Esc, close button and backdrop click', async () => {
+  it('closes on Esc, close button and empty-stage click', async () => {
     const wrapper = mountLightbox('p2');
     await flushPromises();
 
     keydown('Escape');
     expect(lightbox(wrapper).emitted('close')).toHaveLength(1);
 
-    await wrapper.find('.control.close').trigger('click');
+    await wrapper.find('.viewer-close').trigger('click');
     expect(lightbox(wrapper).emitted('close')).toHaveLength(2);
 
-    await wrapper.find('.backdrop').trigger('click');
+    // 舞台空白区（目标=容器自身，非 <img>）点击关闭。
+    await wrapper.find('.image-container').trigger('click');
     expect(lightbox(wrapper).emitted('close')).toHaveLength(3);
   });
 
@@ -198,10 +209,10 @@ describe('photo lightbox (Task 8)', () => {
     expect(img(wrapper).attributes('style')).toContain('scale(1)');
   });
 
-  it('swipe navigates when flat; drag on backdrop does not close', async () => {
+  it('swipe navigates when flat; drag on stage does not close', async () => {
     const wrapper = mountLightbox('p2');
     await flushPromises();
-    const root = wrapper.find('.lightbox');
+    const root = wrapper.find('.photo-viewer');
 
     // 左滑 80px → 下一张。
     root.element.dispatchEvent(pointerEvent('pointerdown', { pointerId: 1, clientX: 200, clientY: 150 }));
@@ -210,11 +221,11 @@ describe('photo lightbox (Task 8)', () => {
     await flushPromises();
     expect(lightbox(wrapper).emitted('update:photoId')).toEqual([['p3']]);
 
-    // 拖拽距离超过阈值后收尾在背景上：click 不关闭。
+    // 拖拽距离超过阈值后收尾在舞台上：click 不关闭。
     root.element.dispatchEvent(pointerEvent('pointerdown', { pointerId: 1, clientX: 200, clientY: 150 }));
     root.element.dispatchEvent(pointerEvent('pointermove', { pointerId: 1, clientX: 100, clientY: 160 }));
     root.element.dispatchEvent(pointerEvent('pointerup', { pointerId: 1, clientX: 100, clientY: 160 }));
-    await wrapper.find('.backdrop').trigger('click');
+    await wrapper.find('.image-container').trigger('click');
     expect(lightbox(wrapper).emitted('close')).toBeUndefined();
   });
 
@@ -297,3 +308,143 @@ describe('photo lightbox (Task 8)', () => {
     expect(img(wrapper).attributes('src')).toBe('http://img.test/p2-browse.jpg?s=3');
   });
 });
+
+describe('photo lightbox dark viewer (UI-02 V04)', () => {
+  beforeEach(() => {
+    localStorage.clear();
+    i18n = createViewerI18n('zh-CN');
+    mockedGetPublicPhotos.mockReset().mockResolvedValue(makeList([makePhoto('p1'), makePhoto('p2'), makePhoto('p3')]));
+    mockedGetPublicPhoto.mockReset();
+    document.body.style.overflow = '';
+  });
+
+  afterEach(() => {
+    while (mounted.length > 0) {
+      mounted.pop()?.unmount();
+    }
+    vi.restoreAllMocks();
+    document.body.style.overflow = '';
+    document.documentElement.className = '';
+  });
+
+  it('shows the loaded-count fallback while more pages remain (no fake total)', async () => {
+    let resolvePage!: (value: PublicPhotoList) => void;
+    mockedGetPublicPhotos.mockReset();
+    mockedGetPublicPhotos
+      .mockResolvedValueOnce(makeList([makePhoto('p1'), makePhoto('p2')], 'cur-1'))
+      .mockReturnValueOnce(
+        new Promise<PublicPhotoList>((resolve) => {
+          resolvePage = resolve;
+        }),
+      );
+    const wrapper = mountLightbox('p2');
+    await flushPromises();
+
+    // 未到末页且接口无 total → 「已加载 N 张」（§5.2），不显示 i/n。
+    expect(wrapper.find('.position-indicator').text()).toBe('已加载 2 张');
+
+    resolvePage(makeList([makePhoto('p3')], null));
+    await flushPromises();
+    // 全部加载完成 → 当前筛选序列 i / n。
+    expect(wrapper.find('.position-indicator').text()).toBe('2 / 3');
+  });
+
+  it('shows photo preview for an unpositioned solo deep-link entry', async () => {
+    const wrapper = mountLightbox('solo-9', { solo: makePhoto('solo-9') });
+    await flushPromises();
+
+    // solo 自然位置未知（首页加载后仍追加在尾部）→ 「照片预览」，不伪造排名。
+    expect(wrapper.find('.position-indicator').text()).toBe('照片预览');
+  });
+
+  it('renders the thumbnail strip window and selects without extra history entries', async () => {
+    const wrapper = mountLightbox('p2');
+    await flushPromises();
+
+    // 3 张全部落在 ±3 窗口内；当前项描边 + aria-current；点击只上抛切换。
+    const thumbs = wrapper.findAll('.thumb');
+    expect(thumbs.map((thumb) => thumb.find('img').attributes('src'))).toEqual([
+      'http://img.test/p1-thumb.jpg?s=1',
+      'http://img.test/p2-thumb.jpg?s=1',
+      'http://img.test/p3-thumb.jpg?s=1',
+    ]);
+    expect(thumbs[1].classes()).toContain('current');
+    expect(thumbs[1].attributes('aria-current')).toBe('true');
+
+    await thumbs[0].trigger('click');
+    expect(lightbox(wrapper).emitted('update:photoId')).toEqual([['p1']]);
+  });
+
+  it('more menu exposes the reduce-motion toggle; Escape closes the menu before the viewer', async () => {
+    const wrapper = mountLightbox('p2');
+    await flushPromises();
+
+    await wrapper.find('.viewer-more').trigger('click');
+    expect(wrapper.find('.more-popover').exists()).toBe(true);
+    const item = wrapper.find('.more-item');
+    expect(item.text()).toContain('减少动画');
+    expect(item.attributes('aria-checked')).toBe('false');
+    await item.trigger('click');
+    expect(wrapper.find('.more-item').attributes('aria-checked')).toBe('true');
+    // 还原模块级偏好单例，避免影响后续用例。
+    await wrapper.find('.more-item').trigger('click');
+
+    keydown('Escape');
+    await flushPromises();
+    expect(wrapper.find('.more-popover').exists()).toBe(false); // 先收菜单
+    expect(lightbox(wrapper).emitted('close')).toBeUndefined(); // 不关查看器
+
+    keydown('Escape');
+    await flushPromises();
+    expect(lightbox(wrapper).emitted('close')).toHaveLength(1);
+  });
+
+  it('moves focus into the dialog on open and returns it to the trigger on close', async () => {
+    const trigger = document.createElement('button');
+    document.body.appendChild(trigger);
+    trigger.focus();
+
+    const wrapper = mountLightbox('p2');
+    // jsdom 下脱离文档的元素 focus() 不改 activeElement：赶在调度器微任务
+    // （rootEl watcher 调 focus）之前同步挂进文档。
+    document.body.appendChild(wrapper.element);
+    await flushPromises();
+
+    const root = wrapper.find('.photo-viewer');
+    expect(root.attributes('role')).toBe('dialog');
+    expect(root.attributes('aria-modal')).toBe('true');
+    expect(root.attributes('tabindex')).toBe('-1');
+    expect(root.attributes('aria-label')).toBe('照片查看器');
+    expect(document.activeElement).toBe(root.element);
+
+    // 手动卸载（绕过 mounted 清单）验证焦点归还触发元素。
+    const index = mounted.indexOf(wrapper);
+    if (index >= 0) mounted.splice(index, 1);
+    wrapper.unmount();
+    expect(document.activeElement).toBe(trigger);
+    trigger.remove();
+  });
+
+  it('locks body scroll while open and restores the previous value on close', async () => {
+    document.body.style.overflow = 'auto';
+    const wrapper = mountLightbox('p2');
+    await flushPromises();
+    expect(document.body.style.overflow).toBe('hidden');
+
+    const index = mounted.indexOf(wrapper);
+    if (index >= 0) mounted.splice(index, 1);
+    wrapper.unmount();
+    expect(document.body.style.overflow).toBe('auto');
+  });
+
+  it('applies dvh viewport height and safe-area insets for the immersive layout', () => {
+    // vitest 不加载 SFC 样式：源级断言（与 viewer-shell 的 token 源级断言同法）。
+    const source = readFileSync(
+      join(dirname(fileURLToPath(import.meta.url)), '..', 'components', 'PhotoLightbox.vue'),
+      'utf8',
+    );
+    expect(source).toContain('100dvh');
+    expect(source).toContain('env(safe-area-inset-top, 0px)');
+    expect(source).toContain('env(safe-area-inset-bottom, 0px)');
+  });
+});
diff --git a/apps/viewer/src/__tests__/photo-action-bar.spec.ts b/apps/viewer/src/__tests__/photo-action-bar.spec.ts
new file mode 100644
index 0000000..ba0ede6
--- /dev/null
+++ b/apps/viewer/src/__tests__/photo-action-bar.spec.ts
@@ -0,0 +1,117 @@
+import { mount, type VueWrapper } from '@vue/test-utils';
+import { nextTick } from 'vue';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import PhotoActionBar from '../components/viewer/PhotoActionBar.vue';
+import { createViewerI18n, type ViewerI18n } from '../i18n';
+
+// UI-02 §5.1/§5.4 底部操作栏单测：Like/Share/Download 三键与标签、计数
+// Intl 格式化、下载关闭时移除整项（剩余均分）、原图二级菜单（▾ 与长按）、
+// 事件上抛（like/share/download(variant)）。
+let i18n: ViewerI18n;
+const mounted: VueWrapper[] = [];
+
+function mountBar(props: {
+  likeCount: number;
+  canDownload?: boolean;
+  canDownloadOriginal?: boolean;
+  isLiking?: boolean;
+}): VueWrapper {
+  const wrapper = mount(PhotoActionBar, {
+    props: {
+      canDownload: false,
+      canDownloadOriginal: false,
+      isLiking: false,
+      ...props,
+    },
+    global: { plugins: [i18n] },
+  });
+  mounted.push(wrapper);
+  return wrapper;
+}
+
+describe('photo action bar (UI-02 V04)', () => {
+  beforeEach(() => {
+    localStorage.clear();
+    i18n = createViewerI18n('zh-CN');
+  });
+
+  afterEach(() => {
+    while (mounted.length > 0) mounted.pop()?.unmount();
+    vi.useRealTimers();
+    vi.restoreAllMocks();
+  });
+
+  it('renders like/share/download as evenly distributed slots with formatted count and hint', () => {
+    const wrapper = mountBar({ likeCount: 1286, canDownload: true });
+
+    // 三个 action-slot flex 均分（下载隐藏时由剩余 slot 自然重排，见下例）。
+    expect(wrapper.findAll('.action-slot')).toHaveLength(3);
+    const labels = wrapper.findAll('.action-label').map((label) => label.text());
+    expect(labels).toEqual(['点赞', '分享', '下载']);
+    // 计数 Intl 分组 + tabular-nums 容器；Like 下方次级提示（§5.1）。
+    expect(wrapper.find('.like-count').text()).toBe('1,286');
+    expect(wrapper.find('.like-hint').text()).toBe('连续点击，为照片点赞');
+  });
+
+  it('removes the download action entirely when downloads are disabled', () => {
+    const wrapper = mountBar({ likeCount: 0, canDownload: false });
+
+    expect(wrapper.find('.download-group').exists()).toBe(false);
+    expect(wrapper.findAll('.action-slot')).toHaveLength(2); // 剩余两键均分栏宽
+    expect(wrapper.findAll('.action-label').map((label) => label.text())).toEqual(['点赞', '分享']);
+  });
+
+  it('emits like and share from the large tap targets', async () => {
+    const wrapper = mountBar({ likeCount: 3 });
+    const buttons = wrapper.findAll('.action-btn');
+    expect(buttons).toHaveLength(2);
+
+    await buttons[0].trigger('click');
+    await buttons[1].trigger('click');
+    expect(wrapper.emitted('like')).toHaveLength(1);
+    expect(wrapper.emitted('share')).toHaveLength(1);
+    expect(wrapper.emitted('download')).toBeUndefined();
+  });
+
+  it('downloads the browse variant directly when original download is disabled', async () => {
+    const wrapper = mountBar({ likeCount: 0, canDownload: true, canDownloadOriginal: false });
+
+    expect(wrapper.find('.download-caret').exists()).toBe(false);
+    await wrapper.find('.download-group .action-btn').trigger('click');
+    expect(wrapper.emitted('download')).toEqual([['browse']]);
+  });
+
+  it('offers browse/original choices via the caret menu', async () => {
+    const wrapper = mountBar({ likeCount: 0, canDownload: true, canDownloadOriginal: true });
+
+    const caret = wrapper.find('.download-caret');
+    expect(caret.attributes('aria-haspopup')).toBe('menu');
+    await caret.trigger('click');
+    const menu = wrapper.find('.download-menu');
+    expect(menu.attributes('role')).toBe('menu');
+    expect(menu.text()).toContain('浏览图');
+    expect(menu.text()).toContain('原图');
+
+    const items = menu.findAll('button');
+    await items[1].trigger('click');
+    expect(wrapper.emitted('download')).toEqual([['original']]);
+  });
+
+  it('long-pressing the download button opens the variant menu instead of firing browse', async () => {
+    vi.useFakeTimers();
+    const wrapper = mountBar({ likeCount: 0, canDownload: true, canDownloadOriginal: true });
+
+    const button = wrapper.find('.download-group .action-btn');
+    await button.trigger('pointerdown');
+    vi.advanceTimersByTime(500);
+    await nextTick(); // 定时器改状态后等一帧再查 DOM
+    expect(wrapper.find('.download-menu').exists()).toBe(true);
+
+    // 长按已展开菜单：紧随的 click 被吞掉，不触发默认浏览图下载。
+    await button.trigger('click');
+    expect(wrapper.emitted('download')).toBeUndefined();
+
+    await wrapper.find('.download-menu button').trigger('click');
+    expect(wrapper.emitted('download')).toEqual([['browse']]);
+  });
+});
diff --git a/apps/viewer/src/__tests__/thumbnail-strip.spec.ts b/apps/viewer/src/__tests__/thumbnail-strip.spec.ts
new file mode 100644
index 0000000..b7d8eab
--- /dev/null
+++ b/apps/viewer/src/__tests__/thumbnail-strip.spec.ts
@@ -0,0 +1,115 @@
+import { mount, type VueWrapper } from '@vue/test-utils';
+import { nextTick } from 'vue';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import ThumbnailStrip, { type ThumbnailItem } from '../components/viewer/ThumbnailStrip.vue';
+import { createViewerI18n, type ViewerI18n } from '../i18n';
+import { reducedMotion } from '../ui/prefs';
+
+// UI-02 §5.3 缩略图条单测：±3 窗口（最多 7 项，首尾自然收缩）、当前项描边与
+// aria-current、点击上抛 select（无浏览器历史副作用）、选中项滚入可见范围
+// （遵守减少动画）、无溢出不渲染渐隐提示。
+function makeItems(count: number): ThumbnailItem[] {
+  return Array.from({ length: count }, (_, i) => ({
+    photoId: `p${i + 1}`,
+    thumbUrl: `http://img.test/p${i + 1}-thumb.jpg`,
+  }));
+}
+
+let i18n: ViewerI18n;
+const mounted: VueWrapper[] = [];
+
+function mountStrip(photos: ThumbnailItem[], currentPhotoId: string | null): VueWrapper {
+  const wrapper = mount(ThumbnailStrip, {
+    props: { photos, currentPhotoId },
+    global: { plugins: [i18n] },
+  });
+  mounted.push(wrapper);
+  return wrapper;
+}
+
+function thumbIds(wrapper: VueWrapper): (string | undefined)[] {
+  return wrapper.findAll('.thumb').map((thumb) => thumb.find('img').attributes('src'));
+}
+
+describe('thumbnail strip (UI-02 V04)', () => {
+  beforeEach(() => {
+    localStorage.clear();
+    i18n = createViewerI18n('zh-CN');
+  });
+
+  afterEach(() => {
+    while (mounted.length > 0) mounted.pop()?.unmount();
+    reducedMotion.value = false;
+    vi.restoreAllMocks();
+  });
+
+  it('renders the current ±3 window (max 7 items) centered on the current photo', () => {
+    const wrapper = mountStrip(makeItems(12), 'p6');
+    // p6 的 ±3 → p3..p9 共 7 项；thumb 变体 URL。
+    expect(thumbIds(wrapper)).toEqual([
+      'http://img.test/p3-thumb.jpg',
+      'http://img.test/p4-thumb.jpg',
+      'http://img.test/p5-thumb.jpg',
+      'http://img.test/p6-thumb.jpg',
+      'http://img.test/p7-thumb.jpg',
+      'http://img.test/p8-thumb.jpg',
+      'http://img.test/p9-thumb.jpg',
+    ]);
+  });
+
+  it('clamps the window at both edges without wrapping or extra fetching', () => {
+    const head = mountStrip(makeItems(12), 'p1');
+    expect(thumbIds(head)[0]).toBe('http://img.test/p1-thumb.jpg');
+    expect(thumbIds(head)).toHaveLength(7);
+
+    const tail = mountStrip(makeItems(12), 'p12');
+    expect(thumbIds(tail)).toHaveLength(7);
+    expect(thumbIds(tail).at(-1)).toBe('http://img.test/p12-thumb.jpg');
+
+    // 少于 7 项全量展示（不加载整个相册补位）。
+    const short = mountStrip(makeItems(3), 'p2');
+    expect(thumbIds(short)).toHaveLength(3);
+  });
+
+  it('highlights the current item with the primary border and aria-current', () => {
+    const wrapper = mountStrip(makeItems(5), 'p3');
+    const current = wrapper.findAll('.thumb')[2];
+    expect(current.classes()).toContain('current');
+    expect(current.attributes('aria-current')).toBe('true');
+    expect(wrapper.findAll('.thumb')[0].attributes('aria-current')).toBeUndefined();
+    // 无障碍名称带序号（第 {n} 张）。
+    expect(current.attributes('aria-label')).toBe('第 3 张');
+  });
+
+  it('emits select with the photoId on click (no browser history side effects)', async () => {
+    const wrapper = mountStrip(makeItems(9), 'p5');
+    // p5 的 ±3 窗口从 p2 起。
+    await wrapper.findAll('.thumb')[0].trigger('click');
+    expect(wrapper.emitted('select')).toEqual([['p2']]);
+  });
+
+  it('scrolls the selected item into view, honoring the reduced-motion preference', async () => {
+    const scrollIntoView = vi.fn();
+    HTMLElement.prototype.scrollIntoView = scrollIntoView;
+
+    reducedMotion.value = false;
+    const wrapper = mountStrip(makeItems(12), 'p6');
+    await nextTick(); // flush:'post' 滚动 watcher 在渲染后微任务执行
+    expect(scrollIntoView).toHaveBeenCalledWith(
+      expect.objectContaining({ behavior: 'smooth', inline: 'center', block: 'nearest' }),
+    );
+
+    scrollIntoView.mockClear();
+    reducedMotion.value = true;
+    await wrapper.setProps({ currentPhotoId: 'p8' });
+    expect(scrollIntoView).toHaveBeenCalledWith(
+      expect.objectContaining({ behavior: 'auto', inline: 'center' }),
+    );
+  });
+
+  it('hides the overflow fades when the track is not scrollable', () => {
+    // jsdom 布局为 0：scrollWidth === clientWidth → 两侧均无渐隐提示。
+    const wrapper = mountStrip(makeItems(3), 'p2');
+    expect(wrapper.find('.thumb-fade').exists()).toBe(false);
+  });
+});
diff --git a/apps/viewer/src/__tests__/viewer-position.spec.ts b/apps/viewer/src/__tests__/viewer-position.spec.ts
new file mode 100644
index 0000000..27862d3
--- /dev/null
+++ b/apps/viewer/src/__tests__/viewer-position.spec.ts
@@ -0,0 +1,41 @@
+import { describe, expect, it } from 'vitest';
+import { positionDisplay } from '../viewer/position';
+
+// UI-02 §5.2 位置计数形态判定（纯数据层）：三种真实回退 + 前瞻 total 形态。
+// 组件侧当前传 total=null（公开端点游标分页无总数）；lightbox.spec 覆盖
+// loaded / index / preview 三种模式的端到端渲染。
+describe('viewer position display fallbacks (UI-02 §5.2)', () => {
+  it('shows i / total only when the API provides an accurate total', () => {
+    expect(positionDisplay({ index: 11, loaded: 24, total: 248, atEnd: false, solo: false })).toEqual({
+      kind: 'total',
+      current: 12,
+      total: 248,
+    });
+  });
+
+  it('shows the loaded count while more pages remain and no total exists', () => {
+    expect(positionDisplay({ index: 2, loaded: 24, total: null, atEnd: false, solo: false })).toEqual({
+      kind: 'loaded',
+      count: 24,
+    });
+  });
+
+  it('shows i / n of the filtered sequence once all pages are loaded', () => {
+    expect(positionDisplay({ index: 4, loaded: 30, total: null, atEnd: true, solo: false })).toEqual({
+      kind: 'index',
+      current: 5,
+      total: 30,
+    });
+  });
+
+  it('never fabricates a position for unpositioned or solo deep-link entries', () => {
+    // solo：即使有准确 total，也不知道目标在筛选序列中的自然位置。
+    expect(positionDisplay({ index: 24, loaded: 25, total: 248, atEnd: true, solo: true })).toEqual({
+      kind: 'preview',
+    });
+    // 下标未知（-1，防御分支）。
+    expect(positionDisplay({ index: -1, loaded: 3, total: null, atEnd: true, solo: false })).toEqual({
+      kind: 'preview',
+    });
+  });
+});
diff --git a/apps/viewer/src/__tests__/viewer-route.spec.ts b/apps/viewer/src/__tests__/viewer-route.spec.ts
index b332687..a7cd890 100644
--- a/apps/viewer/src/__tests__/viewer-route.spec.ts
+++ b/apps/viewer/src/__tests__/viewer-route.spec.ts
@@ -122,7 +122,7 @@ describe('viewer url sync and deep link (Task 8)', () => {
     scrollTo.mockClear();
     keydown('Escape');
     await vi.waitFor(() => expect(router.currentRoute.value.path).toBe('/a/tok-view'));
-    expect(wrapper.find('.lightbox').exists()).toBe(false);
+    expect(wrapper.find('.photo-viewer').exists()).toBe(false);
     expect(scrollTo).toHaveBeenCalledWith(0, 650);
     expect(replaceSpy).toHaveBeenCalledTimes(1); // 关闭未额外 replace
   });
@@ -137,13 +137,13 @@ describe('viewer url sync and deep link (Task 8)', () => {
     const scrollTo = vi.spyOn(window, 'scrollTo').mockImplementation(() => {});
     await wrapper.findAll('.cell')[0].trigger('click');
     await flushPromises();
-    expect(wrapper.find('.lightbox').exists()).toBe(true);
+    expect(wrapper.find('.photo-viewer').exists()).toBe(true);
 
     scrollTo.mockClear();
     router.back(); // 等价浏览器后退（popstate 异步派发）
     await vi.waitFor(() => expect(router.currentRoute.value.path).toBe('/a/tok-view'));
     await flushPromises();
-    expect(wrapper.find('.lightbox').exists()).toBe(false);
+    expect(wrapper.find('.photo-viewer').exists()).toBe(false);
     expect(scrollTo).toHaveBeenCalledWith(0, 320);
   });
 
@@ -164,15 +164,15 @@ describe('viewer url sync and deep link (Task 8)', () => {
     const wrapper = mountApp();
     await flushPromises();
 
-    // 单图先行：列表仍在加载，大图已可看（solo 序列 1/1）。
+    // 单图先行：列表仍在加载，大图已可看（solo 位置未知 → 「照片预览」，§5.2 不伪造排名）。
     expect(mockedGetPublicPhoto).toHaveBeenCalledWith('tok-view', 'p5');
     expect(wrapper.find('img.photo').attributes('src')).toBe('http://img.test/p5-browse.jpg?s=1');
-    expect(wrapper.find('.counter').text()).toBe('1 / 1');
+    expect(wrapper.find('.position-indicator').text()).toBe('照片预览');
 
     // 第 1 页到达（无 p5）→ 深链 watcher 追拉第 2 页 → p5 归位自然顺序（5/5）。
     resolveFirstPage(makeList([makePhoto('p1'), makePhoto('p2'), makePhoto('p3')], 'cur-1'));
     await vi.waitFor(() => expect(wrapper.findAll('.cell')).toHaveLength(5));
-    expect(wrapper.find('.counter').text()).toBe('5 / 5');
+    expect(wrapper.find('.position-indicator').text()).toBe('5 / 5');
 
     // 序列已构成：左切到前一张。
     keydown('ArrowLeft');
@@ -189,7 +189,7 @@ describe('viewer url sync and deep link (Task 8)', () => {
     const wrapper = mountApp();
     await flushPromises();
 
-    expect(wrapper.find('.lightbox').exists()).toBe(false);
+    expect(wrapper.find('.photo-viewer').exists()).toBe(false);
     const notice = wrapper.find('.deep-link-notice[role="alert"]');
     expect(notice.text()).toContain('照片不存在或已下线');
     expect(notice.text()).not.toContain('PHOTO_NOT_PUBLIC'); // 不裸露错误码
diff --git a/apps/viewer/src/components/PhotoLightbox.vue b/apps/viewer/src/components/PhotoLightbox.vue
index 2c49015..813d19e 100644
--- a/apps/viewer/src/components/PhotoLightbox.vue
+++ b/apps/viewer/src/components/PhotoLightbox.vue
@@ -1,39 +1,48 @@
 <script setup lang="ts">
 import { computed, onBeforeUnmount, onMounted, reactive, ref, watch } from 'vue';
 import { useI18n } from 'vue-i18n';
+import type { DownloadVariant } from '../api/client';
 import type { PhotoSequence } from '../feed/sequence';
 import type { DownloadController } from '../download/useDownload';
 import type { LikesController } from '../likes/useLikes';
+import PhotoActionBar from './viewer/PhotoActionBar.vue';
+import ThumbnailStrip, { type ThumbnailItem } from './viewer/ThumbnailStrip.vue';
+import { copyText } from '../support/clipboard';
+import { reducedMotion, toggleReducedMotion } from '../ui/prefs';
+import { positionDisplay } from '../viewer/position';
 import { MIN_SCALE, panBy, resetZoom, wheelFactor, zoomAt, type ZoomState } from '../viewer/zoom';
 
-// 大图查看器（Task 8）：browse URL 全屏展示 + 左右切换（保持列表浏览序列，越过
-// 末尾且 hasMore 时取下一页扩展）+ 滚轮/双指缩放与平移（受控 CSS transform，数学
-// 见 viewer/zoom.ts）+ 签名过期静默重取（复用 sequence.refreshPhotoUrls）。
+// 大图查看器（Task 8 业务编排 + UI-02 V04 深色沉浸布局）：
+//   · 布局层级（§5.1）：顶栏（关闭 × / 位置计数 / ⋯ 菜单）→ 图片舞台（contain
+//     大图 + 边缘 ‹ › 切换 + 粒子/互动占位层）→ 缩略图条 → 底部操作栏；
+//   · 业务逻辑不变：browse URL 展示、保持列表序列的左右切换（越过末尾且
+//     hasMore 时翻页扩展）、zoom.ts 缩放/平移、签名过期静默重取（复用
+//     sequence.refreshPhotoUrls）、下载两级开关与微信引导（useDownload）、
+//     点赞乐观计数（useLikes）；
+//   · 位置计数（§5.2 真实回退）：见 viewer/position.ts——深链 solo 显示
+//     「照片预览」，无 total 未到末页显示「已加载 N 张」，全部加载完成才
+//     显示筛选序列 i/n；当前 API 无 total，不伪造总数；
+//   · 模态可用性：打开锁 body 滚动、焦点进入对话框并困于其内（Tab 循环）、
+//     关闭/卸载时焦点回到触发元素；Esc 先收菜单再关查看器；左右键在菜单
+//     焦点内不抢占（§5.3）；
+//   · 关闭回位（滚动锚点 savedScrollY）与 URL push/replace/back 语义由
+//     ActivityPage 负责（见 ActivityPage 注释）。
 //
-// 状态归属：序列数据/分页在 ActivityPage 创建的 PhotoSequence（共享 composable），
-// 本组件只持视图态（缩放/平移、加载失败标记、扩展中标记）；当前照片以 photoId
-// （v-model）为准而非下标——序列追加/solo 归位/条目移除都会移动下标，photoId 键
-// 控让重排自动保持指向同一张照片。
-//
-// 手势（Pointer Events，无第三方依赖）：
-//   · 双指：捏合缩放（transform 不动点 = 手势中心）+ 中点漂移平移；
+// 手势（Pointer Events，无第三方依赖；与 V04 布局的协作）：
+//   · 手势绑定在根元素，但顶栏/缩略图条/底部操作栏（data-lightbox-chrome）
+//     内的指针不参与手势——条带横滚、按钮点击不会误触轻扫切图；
+//   · 双指：捏合缩放（不动点 = 手势中心）+ 中点漂移平移；
 //   · 单指且 scale>1：拖拽平移；scale=1：横向轻扫切换上一张/下一张；
-//   · 双击（鼠标 dblclick / 触控双 tap）：复位缩放；
-//   · 滚轮（无需 ctrl）：以光标为不动点缩放；Esc/关闭按钮/背景点击关闭。
-//
-// 下载（P4a Task 4）：工具栏入口按相册两级开关渲染（控制器 canDownload /
-// canDownloadOriginal；download prop 缺省不渲染——组件单测/降级组装）。原图
-// 可下时为分体按钮（主按钮=浏览图 + ▾ 菜单两选项）；微信内置浏览器由控制器
-// 判定并改走引导浮层（长按保存 + 复制深链）。
-//
-// 关闭回位（滚动锚点）与 URL 同步由 ActivityPage 负责（见 ActivityPage 注释）。
+//   · 双击（dblclick / 触控双 tap）：复位缩放；滚轮：以光标为不动点缩放
+//     （缩略图条 data-native-scroll 区域内的滚轮留给条带横滚）；
+//   · 舞台空白区（非图片）点击关闭；手势位移后的 click 不关闭。
 
 const props = defineProps<{
   sequence: PhotoSequence;
   photoId: string;
-  /** 点赞控制器（Task 10）：缺省不渲染点赞位（组件单测/降级组装）。 */
+  /** 点赞控制器（Task 10）：缺省时 Like 位退化为静态计数（组件单测/降级组装）。 */
   likes?: LikesController;
-  /** 下载控制器（P4a Task 4）：缺省不渲染下载位（组件单测/降级组装）。 */
+  /** 下载控制器（P4a Task 4）：缺省时不渲染下载位（组件单测/降级组装）。 */
   download?: DownloadController;
 }>();
 
@@ -54,6 +63,28 @@ const hasPrev = computed(() => index.value > 0);
 // 末张且仍有下一页 → 允许继续向右（导航触发序列扩展）。
 const hasNext = computed(() => index.value < total.value - 1 || props.sequence.hasMore);
 
+// —— 位置计数（§5.2）：形态判定在 viewer/position.ts，此处只拼接文案 ——
+
+const positionText = computed(() => {
+  const display = positionDisplay({
+    index: index.value,
+    loaded: photos.value.length,
+    // 当前公开端点为游标分页（CursorPageMeta 无 total）——不伪造总数；
+    // 接口将来提供准确 total 时改传实值即得「12 / 248」形态。
+    total: null,
+    atEnd: !props.sequence.hasMore,
+    solo: props.sequence.isSolo(props.photoId),
+  });
+  switch (display.kind) {
+    case 'preview':
+      return t('viewer.photoPreview');
+    case 'loaded':
+      return t('viewer.loadedCount', { count: display.count });
+    default:
+      return `${display.current} / ${display.total}`;
+  }
+});
+
 // —— 视图状态（按 photoId；切换照片即复位） ——
 
 /** 图片单次重试的缓存击穿键：重试按钮点击后 +1 强制 <img> 重挂载重触发加载。 */
@@ -76,24 +107,30 @@ watch(
 
 const zoom = reactive<ZoomState>({ ...resetZoom() });
 const rootEl = ref<HTMLElement | null>(null);
+/** 舞台（图片容器）：缩放不动点坐标系的原点（图片经 flex 居中于其中）。 */
+const stageEl = ref<HTMLElement | null>(null);
 
 const imgStyle = computed(() => ({
   transform: `translate(${zoom.tx}px, ${zoom.ty}px) scale(${zoom.scale})`,
 }));
 
-/** 手势中心（相对图片未变换时中心的坐标）：图片经 flex 居中，未变换中心 = 容器中心。 */
+/** 手势中心（相对图片未变换时中心的坐标）：图片经 flex 居中，未变换中心 = 舞台中心。 */
 function center(): { x: number; y: number } {
-  const rect = rootEl.value?.getBoundingClientRect();
+  const rect = stageEl.value?.getBoundingClientRect();
   if (rect === undefined) return { x: 0, y: 0 };
   return { x: rect.left + rect.width / 2, y: rect.top + rect.height / 2 };
 }
 
 function onWheel(event: WheelEvent): void {
+  // 缩略图条等原生滚动区（data-native-scroll）内的滚轮留给自身横滚。
+  if (event.target instanceof HTMLElement && event.target.closest('[data-native-scroll]') !== null) return;
+  event.preventDefault();
   const { x, y } = center();
   Object.assign(zoom, zoomAt({ ...zoom }, wheelFactor(event.deltaY), event.clientX - x, event.clientY - y));
 }
 
-function onDblClick(): void {
+function onDblClick(event: MouseEvent): void {
+  if (inChrome(event.target)) return;
   Object.assign(zoom, resetZoom());
 }
 
@@ -104,11 +141,21 @@ let pinchDistance = 0;
 let pinchMid = { x: 0, y: 0 };
 let swipe: { x: number; y: number; dx: number; dy: number } | null = null;
 let lastTap = { time: 0, x: 0, y: 0 };
-/** 手势期间发生过位移：抑制手势收尾时的背景 click 误关闭。 */
+/** 手势期间发生过位移：抑制手势收尾时的舞台 click 误关闭。 */
 let dragged = false;
 
 const SWIPE_MIN_DISTANCE = 50;
 
+/** 顶栏/缩略图条/底部操作栏（data-lightbox-chrome）：不参与手势与双击复位。 */
+function inChrome(target: EventTarget | null): boolean {
+  return target instanceof HTMLElement && target.closest('[data-lightbox-chrome]') !== null;
+}
+
+/** 菜单（role=menu）焦点内左右键不抢占切图（§5.3）。 */
+function inMenu(target: EventTarget | null): boolean {
+  return target instanceof HTMLElement && target.closest('[role="menu"]') !== null;
+}
+
 function pointerPair(): { a: { x: number; y: number }; b: { x: number; y: number } } | null {
   if (pointers.size < 2) return null;
   const [first, second] = pointers.values();
@@ -121,6 +168,7 @@ function distance(a: { x: number; y: number }, b: { x: number; y: number }): num
 }
 
 function onPointerDown(event: PointerEvent): void {
+  if (inChrome(event.target)) return;
   pointers.set(event.pointerId, { x: event.clientX, y: event.clientY });
   dragged = false;
 
@@ -167,7 +215,7 @@ function onPointerMove(event: PointerEvent): void {
   }
 
   if (zoom.scale > MIN_SCALE) {
-    // 单指平移（scale>1）。
+    // 单指平移（scale>1）：平移期间不触发轻扫切图（§5.3）。
     Object.assign(zoom, panBy({ ...zoom }, current.x - previous.x, current.y - previous.y));
     dragged = true;
   } else if (swipe !== null) {
@@ -204,23 +252,52 @@ function onPointerEnd(event: PointerEvent): void {
   }
 }
 
-function onBackdropClick(): void {
-  if (dragged) return; // 手势收尾的 click 不关闭
+/** 舞台空白区（目标=容器自身，非图片/占位）点击关闭；手势位移后的 click 不关闭。 */
+function onStageClick(event: MouseEvent): void {
+  if (dragged) return;
+  if (event.target !== event.currentTarget) return;
   emit('close');
 }
 
-// —— 键盘 ——
+// —— 键盘：Esc 关闭（菜单开时先收菜单）、←→ 切换、Tab 焦点困于对话框 ——
 
 function onKeydown(event: KeyboardEvent): void {
   if (event.key === 'Escape') {
     event.preventDefault();
+    if (moreMenuOpen.value) {
+      moreMenuOpen.value = false;
+      return;
+    }
     emit('close');
-  } else if (event.key === 'ArrowLeft') {
+  } else if (event.key === 'ArrowLeft' || event.key === 'ArrowRight') {
+    if (inMenu(event.target)) return;
     event.preventDefault();
-    void goTo(index.value - 1);
-  } else if (event.key === 'ArrowRight') {
+    void goTo(event.key === 'ArrowLeft' ? index.value - 1 : index.value + 1);
+  }
+}
+
+/** Tab 循环限制在对话框内（模态焦点不穿透，§5.3）。 */
+function onTrapTab(event: KeyboardEvent): void {
+  const root = rootEl.value;
+  if (root === null) return;
+  const focusables = Array.from(
+    root.querySelectorAll<HTMLElement>('button:not([disabled]), [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'),
+  );
+  if (focusables.length === 0) {
     event.preventDefault();
-    void goTo(index.value + 1);
+    return;
+  }
+  const first = focusables[0];
+  const last = focusables[focusables.length - 1];
+  const active = document.activeElement;
+  if (event.shiftKey) {
+    if (active === first || !root.contains(active)) {
+      event.preventDefault();
+      last.focus();
+    }
+  } else if (active === last || !root.contains(active)) {
+    event.preventDefault();
+    first.focus();
   }
 }
 
@@ -243,6 +320,14 @@ async function goTo(targetIndex: number): Promise<void> {
   emit('update:photoId', target.photoId);
 }
 
+/** 缩略图条选择：与手势/键盘共用 goTo 入口（update:photoId → 父级 replace 路由，
+   * 不新增浏览器历史）。 */
+function selectThumbnail(photoId: string): void {
+  if (photoId === props.photoId) return;
+  const targetIndex = photos.value.findIndex((item) => item.photoId === photoId);
+  if (targetIndex >= 0) void goTo(targetIndex);
+}
+
 // 相邻预取（±1 browse URL）+ 临近末尾预拉下一页，让右切更顺滑。
 watch(
   () => [props.photoId, photos.value] as const,
@@ -266,32 +351,54 @@ function preload(url: string): void {
 
 // —— 点赞（Task 10）：乐观 +1 与心跳动画由 LikesController 承担 ——
 
+const displayLikeCount = computed(() => {
+  if (photo.value === null) return 0;
+  return props.likes !== undefined ? props.likes.displayFor(photo.value) : photo.value.likeCount;
+});
+
 function likeCurrent(): void {
   if (photo.value === null || props.likes === undefined) return;
   props.likes.like(photo.value.photoId);
 }
 
-// —— 下载（P4a Task 4）：菜单开合随照片切换/关闭复位 ——
+// —— 下载（P4a Task 4）：入口与二级菜单在 PhotoActionBar，控制器编排在此 ——
 
-const downloadMenuOpen = ref(false);
+const canDownload = computed(() => props.download !== undefined && props.download.canDownload);
+const canDownloadOriginal = computed(() => canDownload.value && props.download !== undefined && props.download.canDownloadOriginal);
 
-watch(
-  () => props.photoId,
-  () => {
-    downloadMenuOpen.value = false;
-  },
-);
-
-/** 菜单选项点击：收起菜单后发起对应 variant 下载。 */
-function pickDownload(variant: 'browse' | 'original'): void {
-  downloadMenuOpen.value = false;
+function onDownloadVariant(variant: DownloadVariant): void {
   void props.download?.download(variant);
 }
 
-/** 主按钮：无原图位时直下浏览图；有原图位时也直下浏览图（菜单提供两项）。 */
-function downloadBrowse(): void {
-  downloadMenuOpen.value = false;
-  void props.download?.download('browse');
+// —— 分享（V04 最小实现：复制当前照片深链——路由已同步 /p/:photoId；
+//    navigator.share 编排与语言参数属 Task 5/V05） ——
+
+const shareState = ref<'idle' | 'copied' | 'failed'>('idle');
+const shareUrlText = ref('');
+let shareResetTimer: ReturnType<typeof setTimeout> | undefined;
+
+async function shareCurrent(): Promise<void> {
+  shareUrlText.value = window.location.href;
+  const copied = await copyText(shareUrlText.value);
+  shareState.value = copied ? 'copied' : 'failed';
+  if (shareResetTimer !== undefined) clearTimeout(shareResetTimer);
+  // 失败时保留可选中文本（不自动消失），成功反馈数秒后收起。
+  if (copied) {
+    shareResetTimer = setTimeout(() => {
+      shareState.value = 'idle';
+    }, 3000);
+  }
+}
+
+// —— 顶栏「⋯」更多菜单（§5.1：必须有实际功能——减少动画开关） ——
+
+const moreMenuOpen = ref(false);
+const moreRootEl = ref<HTMLElement | null>(null);
+
+function onOuterPointerDown(event: PointerEvent): void {
+  if (moreMenuOpen.value && moreRootEl.value !== null && !moreRootEl.value.contains(event.target as Node)) {
+    moreMenuOpen.value = false;
+  }
 }
 
 // —— 签名过期/下线处理 ——
@@ -324,12 +431,38 @@ function retryFailed(): void {
   retryCount.value += 1; // 强制 <img> 重挂载，重新触发加载/错误链
 }
 
+// —— 模态可用性：body 滚动锁 + 焦点进入/困住/归还（§5.1/§5.3） ——
+
+let savedBodyOverflow = '';
+let savedFocus: HTMLElement | null = null;
+let focusClaimed = false;
+
+// 根节点渲染时（深链下序列就位前组件先挂载、photo 后到）：焦点进入对话框。
+watch(rootEl, (el) => {
+  if (el === null || focusClaimed) return;
+  focusClaimed = true;
+  savedFocus = document.activeElement instanceof HTMLElement ? document.activeElement : null;
+  el.focus();
+});
+
+const thumbItems = computed<ThumbnailItem[]>(() =>
+  photos.value.map((item) => ({ photoId: item.photoId, thumbUrl: item.thumb.url })),
+);
+
 onMounted(() => {
   window.addEventListener('keydown', onKeydown);
+  document.addEventListener('pointerdown', onOuterPointerDown, true);
+  savedBodyOverflow = document.body.style.overflow;
+  document.body.style.overflow = 'hidden'; // 锁背景滚动（§5.1）
 });
 
 onBeforeUnmount(() => {
   window.removeEventListener('keydown', onKeydown);
+  document.removeEventListener('pointerdown', onOuterPointerDown, true);
+  document.body.style.overflow = savedBodyOverflow;
+  if (shareResetTimer !== undefined) clearTimeout(shareResetTimer);
+  // 焦点归还触发元素（瀑布流单元格；深链直达时为 body——无可归还则不动）。
+  if (savedFocus !== null && savedFocus.isConnected) savedFocus.focus();
 });
 </script>
 
@@ -337,112 +470,135 @@ onBeforeUnmount(() => {
   <div
     v-if="photo !== null"
     ref="rootEl"
-    class="lightbox"
+    class="photo-viewer"
     role="dialog"
     aria-modal="true"
-    :aria-label="t('viewer.title')"
-    @wheel.prevent="onWheel"
+    :aria-label="t('viewer.photoViewer')"
+    tabindex="-1"
+    @wheel="onWheel"
     @pointerdown="onPointerDown"
     @pointermove="onPointerMove"
     @pointerup="onPointerEnd"
     @pointercancel="onPointerEnd"
     @pointerleave="onPointerEnd"
     @dblclick="onDblClick"
+    @keydown.tab="onTrapTab"
   >
-    <div class="backdrop" @click="onBackdropClick" />
-
-    <img
-      v-if="!failedIds.has(photo.photoId)"
-      :key="`${photo.photoId}:${retryCount}`"
-      class="photo"
-      :src="photo.browse.url"
-      :alt="t('route.photoLabel')"
-      :style="imgStyle"
-      draggable="false"
-      @error="onImgError"
-    >
-    <div v-else class="img-failed" role="alert">
-      <p>{{ t('viewer.loadFailed') }}</p>
-      <button type="button" @click="retryFailed">{{ t('album.retry') }}</button>
-    </div>
-
-    <header class="bar">
-      <span class="counter">{{ t('viewer.counter', { current: index + 1, total }) }}</span>
-      <button
-        v-if="likes !== undefined"
-        type="button"
-        class="control like-button"
-        :aria-label="t('viewer.like')"
-        @click="likeCurrent"
-      >
-        <span :key="likes.popNonce(photo.photoId)" class="heart" aria-hidden="true">♥</span>
-        <span class="like-count">{{ likes.displayFor(photo) }}</span>
+    <!-- 顶栏（§5.1：52-56px 深色半透明）：关闭 / 位置计数 / ⋯ 更多菜单 -->
+    <header class="viewer-topbar" data-lightbox-chrome>
+      <button type="button" class="viewer-close" :aria-label="t('viewer.close')" @click="emit('close')">
+        <svg viewBox="0 0 24 24" aria-hidden="true" focusable="false">
+          <path d="M6 6l12 12" />
+          <path d="M18 6 6 18" />
+        </svg>
       </button>
-      <span v-else class="likes">{{ t('viewer.likeCount', { count: photo.likeCount }) }}</span>
-      <!-- 下载（P4a Task 4）：两级开关驱动——都关无入口；browse 单按钮；
-           original 可下 → 分体按钮（主=浏览图 + ▾ 菜单两项）。 -->
-      <div
-        v-if="download !== undefined && download.canDownload"
-        class="download-group"
-      >
+      <p class="position-indicator">{{ positionText }}</p>
+      <div ref="moreRootEl" class="more-menu">
         <button
           type="button"
-          class="control download"
-          :disabled="download.busy"
-          :aria-label="t('download.action')"
-          @click="downloadBrowse"
+          class="viewer-more"
+          :aria-label="t('viewer.more')"
+          aria-haspopup="menu"
+          :aria-expanded="moreMenuOpen"
+          @click="moreMenuOpen = !moreMenuOpen"
         >
-          {{ download.busy ? t('download.busy') : t('download.action') }}
+          <svg viewBox="0 0 24 24" aria-hidden="true" focusable="false">
+            <circle cx="5" cy="12" r="2" fill="currentColor" />
+            <circle cx="12" cy="12" r="2" fill="currentColor" />
+            <circle cx="19" cy="12" r="2" fill="currentColor" />
+          </svg>
         </button>
-        <button
-          v-if="download.canDownloadOriginal"
-          type="button"
-          class="control download-caret"
-          :aria-label="t('download.options')"
-          :aria-expanded="downloadMenuOpen"
-          @click="downloadMenuOpen = !downloadMenuOpen"
-        >
-          ▾
-        </button>
-        <div v-if="downloadMenuOpen && download.canDownloadOriginal" class="download-menu" role="menu">
-          <button type="button" role="menuitem" @click="pickDownload('browse')">
-            {{ t('download.action') }}
-          </button>
-          <button type="button" role="menuitem" @click="pickDownload('original')">
-            {{ t('download.original') }}
+        <div v-if="moreMenuOpen" class="more-popover" role="menu" :aria-label="t('viewer.more')">
+          <button
+            type="button"
+            class="more-item"
+            role="menuitemcheckbox"
+            :aria-checked="reducedMotion"
+            @click="toggleReducedMotion"
+          >
+            <span class="more-check" aria-hidden="true">{{ reducedMotion ? '✓' : '' }}</span>
+            {{ t('viewer.reduceMotion') }}
           </button>
         </div>
       </div>
-      <button type="button" class="control close" :aria-label="t('viewer.close')" @click="emit('close')">
-        ✕
-      </button>
     </header>
 
-    <button
-      type="button"
-      class="control nav prev"
-      :disabled="!hasPrev"
-      :aria-label="t('viewer.previous')"
-      @click="goTo(index - 1)"
-    >
-      ‹
-    </button>
-    <button
-      type="button"
-      class="control nav next"
-      :disabled="!hasNext"
-      :aria-label="t('viewer.next')"
-      @click="goTo(index + 1)"
-    >
-      ›
-    </button>
+    <!-- 图片舞台（flex:1）：contain 大图 + 边缘切换 + 粒子/互动占位层 -->
+    <main class="viewer-stage">
+      <div ref="stageEl" class="image-container" @click="onStageClick">
+        <img
+          v-if="!failedIds.has(photo.photoId)"
+          :key="`${photo.photoId}:${retryCount}`"
+          class="photo"
+          :src="photo.browse.url"
+          :alt="t('route.photoLabel')"
+          :style="imgStyle"
+          draggable="false"
+          @error="onImgError"
+        >
+        <div v-else class="img-failed" role="alert">
+          <p>{{ t('viewer.loadFailed') }}</p>
+          <button type="button" @click="retryFailed">{{ t('album.retry') }}</button>
+        </div>
+      </div>
 
-    <p v-if="extending" class="loading">{{ t('album.loading') }}</p>
+      <button
+        type="button"
+        class="nav prev"
+        :disabled="!hasPrev"
+        :aria-label="t('viewer.previous')"
+        @click="goTo(index - 1)"
+      >
+        <svg viewBox="0 0 24 24" aria-hidden="true" focusable="false">
+          <path d="m15 18-6-6 6-6" />
+        </svg>
+      </button>
+      <button
+        type="button"
+        class="nav next"
+        :disabled="!hasNext"
+        :aria-label="t('viewer.next')"
+        @click="goTo(index + 1)"
+      >
+        <svg viewBox="0 0 24 24" aria-hidden="true" focusable="false">
+          <path d="m9 6 6 6-6 6" />
+        </svg>
+      </button>
 
-    <!-- 下载失败轻提示（端点失败/网络；DOWNLOAD_DISABLED 专属文案；可重点击重试）。 -->
-    <p v-if="download !== undefined && download.failed" class="download-failed" role="alert">
-      {{ t(download.failed) }}
-    </p>
+      <!-- 心形粒子层（Task 5 / V05 填充）：装饰性、不可交互 -->
+      <div class="heart-particles-zone" aria-hidden="true" style="pointer-events: none" />
+      <!-- 跨照片互动提示层（Task 5 / V05 填充）：底部操作栏上方安全区 -->
+      <div class="interaction-notice-zone" />
+
+      <div class="stage-notices">
+        <p v-if="extending" class="loading">{{ t('album.loading') }}</p>
+        <!-- 分享反馈轻提示（复制成功/失败；失败保留可选中文本） -->
+        <p v-if="shareState !== 'idle'" class="share-status" role="status">
+          {{ shareState === 'copied' ? t('viewer.shareCopied') : t('viewer.shareCopyFailed') }}
+          <span v-if="shareState === 'failed'" class="share-url">{{ shareUrlText }}</span>
+        </p>
+        <!-- 下载失败轻提示（端点失败/网络；DOWNLOAD_DISABLED 专属文案）。 -->
+        <p v-if="download !== undefined && download.failed" class="download-failed" role="alert">
+          {{ t(download.failed) }}
+        </p>
+      </div>
+    </main>
+
+    <!-- 缩略图条（§5.3）：当前 ±3 窗口；点击选择（不新增历史） -->
+    <ThumbnailStrip :photos="thumbItems" :current-photo-id="photoId" @select="selectThumbnail" />
+
+    <!-- 底部操作栏（§5.1：88-104px + 安全区）：Like / Share / Download -->
+    <footer class="viewer-actionbar" data-lightbox-chrome>
+      <PhotoActionBar
+        :like-count="displayLikeCount"
+        :like-pop="likes !== undefined && photo !== null ? likes.popNonce(photo.photoId) : 0"
+        :can-download="canDownload"
+        :can-download-original="canDownloadOriginal"
+        @like="likeCurrent"
+        @share="shareCurrent"
+        @download="onDownloadVariant"
+      />
+    </footer>
 
     <!-- 微信内置浏览器引导（P4a Task 4）：替代直接下载——长按保存 + 复制深链。 -->
     <div
@@ -477,21 +633,130 @@ onBeforeUnmount(() => {
 </template>
 
 <style scoped>
-/* 极简基线样式：视觉打磨留待 P4a。 */
-.lightbox {
+/* —— UI-02 V04 深色沉浸布局（§5.1）：dvh + 安全区；token 经祖先 .viewer-shell
+   * 提供，独立挂载（无 shell）时 var() 回退同值 —— */
+.photo-viewer {
   position: fixed;
   inset: 0;
   z-index: 100;
+  height: 100vh;
+  height: 100dvh;
+  display: flex;
+  flex-direction: column;
+  background: var(--viewer-dark-bg, #0e1218);
+  color: #ffffff;
+  user-select: none;
+}
+.photo-viewer:focus {
+  outline: none;
+}
+
+/* 顶栏：grid 三列（44px | 1fr 居中计数 | 44px），半透明深色。 */
+.viewer-topbar {
+  flex: none;
+  display: grid;
+  grid-template-columns: var(--viewer-touch-target, 44px) 1fr var(--viewer-touch-target, 44px);
+  align-items: center;
+  min-height: 52px;
+  padding: 0 8px;
+  padding-top: env(safe-area-inset-top, 0px);
+  background: rgba(14, 18, 24, 0.72);
+}
+.viewer-close,
+.viewer-more {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: var(--viewer-touch-target, 44px);
+  height: var(--viewer-touch-target, 44px);
+  border: none;
+  border-radius: 50%;
+  background: transparent;
+  color: #ffffff;
+  cursor: pointer;
+}
+.viewer-close:hover,
+.viewer-more:hover {
+  background: rgba(255, 255, 255, 0.1);
+}
+.viewer-close:focus-visible,
+.viewer-more:focus-visible {
+  outline: 2px solid var(--viewer-primary, #1a73e8);
+}
+.viewer-close svg,
+.viewer-more svg {
+  width: 22px;
+  height: 22px;
+  fill: none;
+  stroke: currentColor;
+  stroke-width: 2;
+  stroke-linecap: round;
+}
+.position-indicator {
+  margin: 0;
+  text-align: center;
+  font-size: 0.875rem;
+  color: rgba(255, 255, 255, 0.92);
+  font-variant-numeric: tabular-nums;
+}
+.more-menu {
+  position: relative;
+  justify-self: end;
+}
+.more-popover {
+  position: absolute;
+  top: calc(100% + 2px);
+  right: 0;
+  z-index: 6;
+  display: grid;
+  min-width: 176px;
+  border: 1px solid rgba(255, 255, 255, 0.12);
+  border-radius: 12px;
+  background: rgba(22, 28, 36, 0.96);
+  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
+  padding: 4px;
+}
+.more-item {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  min-height: var(--viewer-touch-target, 44px);
+  border: none;
+  border-radius: 8px;
+  background: transparent;
+  color: #ffffff;
+  padding: 0 12px;
+  font-size: 0.875rem;
+  text-align: left;
+  cursor: pointer;
+}
+.more-item:hover {
+  background: rgba(255, 255, 255, 0.08);
+}
+.more-item:focus-visible {
+  outline: 2px solid var(--viewer-primary, #1a73e8);
+}
+.more-check {
+  display: inline-block;
+  width: 1em;
+  color: var(--viewer-primary, #1a73e8);
+  font-weight: 700;
+}
+
+/* 舞台：占剩余空间；contain 完整大图（不裁切）；手势区 touch-action none。 */
+.viewer-stage {
+  position: relative;
+  flex: 1;
+  min-height: 0;
+  overflow: hidden;
+  touch-action: none;
+}
+.image-container {
+  position: absolute;
+  inset: 0;
   display: flex;
   align-items: center;
   justify-content: center;
-  touch-action: none;
-  user-select: none;
-}
-.backdrop {
-  position: absolute;
-  inset: 0;
-  background: rgba(17, 24, 39, 0.92);
 }
 .photo {
   position: relative;
@@ -515,139 +780,118 @@ onBeforeUnmount(() => {
   padding: 4px 12px;
   cursor: pointer;
 }
-.bar {
+.nav {
   position: absolute;
-  top: 0;
+  top: 50%;
+  transform: translateY(-50%);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: var(--viewer-touch-target, 44px);
+  height: var(--viewer-touch-target, 44px);
+  border: none;
+  border-radius: 50%;
+  background: rgba(255, 255, 255, 0.1);
+  color: #ffffff;
+  cursor: pointer;
+}
+.nav:hover:not(:disabled) {
+  background: rgba(255, 255, 255, 0.2);
+}
+.nav:focus-visible {
+  outline: 2px solid var(--viewer-primary, #1a73e8);
+}
+.nav:disabled {
+  opacity: 0.3;
+  cursor: default;
+}
+.nav svg {
+  width: 28px;
+  height: 28px;
+  fill: none;
+  stroke: currentColor;
+  stroke-width: 2;
+  stroke-linecap: round;
+  stroke-linejoin: round;
+}
+.nav.prev {
+  left: 8px;
+}
+.nav.next {
+  right: 8px;
+}
+
+/* 粒子/互动占位层（Task 5 填充）：舞台右侧上浮 / 操作栏上方安全区。 */
+.heart-particles-zone {
+  position: absolute;
+  inset: 0;
+  overflow: hidden;
+}
+.interaction-notice-zone {
+  position: absolute;
+  bottom: 12px;
+  left: 16px;
+  right: 16px;
+  display: flex;
+  flex-direction: column;
+  align-items: flex-start;
+  gap: 6px;
+  pointer-events: none;
+}
+.stage-notices {
+  position: absolute;
+  bottom: 12px;
   left: 0;
   right: 0;
   display: flex;
+  flex-direction: column;
   align-items: center;
-  gap: 16px;
-  padding: 10px 16px;
-  color: #f9fafb;
-  background: linear-gradient(rgba(0, 0, 0, 0.45), transparent);
+  gap: 8px;
+  pointer-events: none;
+  z-index: 4;
 }
-.counter {
-  font-variant-numeric: tabular-nums;
-}
-.likes {
+.loading {
+  margin: 0;
   color: #d1d5db;
-  font-size: 0.875rem;
 }
-.like-button {
-  display: inline-flex;
-  align-items: center;
-  gap: 6px;
-  border-radius: 999px;
-  padding: 4px 12px;
-  font-size: 0.9rem;
-  border: 1px solid rgba(249, 250, 251, 0.35);
+.share-status {
+  margin: 0;
+  border-radius: var(--viewer-radius-pill, 20px);
+  background: rgba(22, 28, 36, 0.92);
+  color: #f3f4f6;
+  padding: 6px 16px;
+  font-size: 0.8125rem;
+  pointer-events: auto;
+  max-width: min(92%, 480px);
 }
-.like-button .heart {
-  color: #ef4444;
-  display: inline-block;
-}
-/* :key 重挂触发心跳放大；「减少动画」时禁用（数字仍即时跳动）。 */
-.like-button .heart {
-  animation: heart-pop 400ms ease-out;
-}
-.like-count {
-  font-variant-numeric: tabular-nums;
-}
-@keyframes heart-pop {
-  0% {
-    transform: scale(1);
-  }
-  40% {
-    transform: scale(1.6);
-  }
-  100% {
-    transform: scale(1);
-  }
-}
-.viewer-reduced-motion .like-button .heart {
-  animation: none;
-}
-.control {
-  border: none;
-  background: rgba(17, 24, 39, 0.55);
-  color: #f9fafb;
-  cursor: pointer;
-}
-.control:disabled {
-  opacity: 0.35;
-  cursor: default;
-}
-.control.close {
-  margin-left: auto;
-  font-size: 1.1rem;
-  border-radius: 6px;
-  padding: 4px 10px;
-}
-/* —— 下载（P4a Task 4）—— */
-.download-group {
-  position: relative;
-  display: inline-flex;
-  align-items: center;
-}
-.control.download {
-  border: 1px solid rgba(249, 250, 251, 0.35);
-  border-radius: 999px 0 0 999px;
-  padding: 4px 12px;
-  font-size: 0.9rem;
-}
-.control.download:disabled {
-  opacity: 0.55;
-  cursor: default;
-}
-.control.download-caret {
-  border: 1px solid rgba(249, 250, 251, 0.35);
-  border-left: none;
-  border-radius: 0 999px 999px 0;
-  padding: 4px 8px;
-  font-size: 0.8rem;
-}
-.download-menu {
-  position: absolute;
-  top: calc(100% + 6px);
-  right: 0;
-  display: grid;
-  min-width: 9em;
-  border-radius: 8px;
-  background: rgba(17, 24, 39, 0.96);
-  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
-  overflow: hidden;
-  z-index: 2;
-}
-.download-menu button {
-  border: none;
-  background: transparent;
-  color: #f9fafb;
-  text-align: left;
-  padding: 8px 14px;
-  font-size: 0.9rem;
-  cursor: pointer;
-}
-.download-menu button:hover {
-  background: rgba(255, 255, 255, 0.08);
+.share-url {
+  user-select: all;
+  word-break: break-all;
+  color: #9fc3f5;
 }
 .download-failed {
-  position: absolute;
-  bottom: 52px;
-  left: 50%;
-  transform: translateX(-50%);
   margin: 0;
-  border-radius: 8px;
+  border-radius: var(--viewer-radius-pill, 20px);
   background: rgba(185, 28, 28, 0.92);
   color: #fef2f2;
-  padding: 6px 14px;
-  font-size: 0.875rem;
+  padding: 6px 16px;
+  font-size: 0.8125rem;
 }
+
+/* 底部操作栏容器：安全区 padding；按钮编排（Like/Share/Download）在
+ * PhotoActionBar（§5.4：下载关闭移除整项并均分剩余栏宽）。 */
+.viewer-actionbar {
+  flex: none;
+  padding: 6px 12px;
+  padding-bottom: calc(6px + env(safe-area-inset-bottom, 0px));
+  background: rgba(14, 18, 24, 0.72);
+}
+
 /* —— 微信引导浮层 —— */
 .wechat-guide {
   position: absolute;
   inset: 0;
-  z-index: 3;
+  z-index: 8;
   display: flex;
   align-items: center;
   justify-content: center;
@@ -703,28 +947,4 @@ onBeforeUnmount(() => {
   font-size: 0.8rem;
   color: #6b7280;
 }
-.control.nav {
-  position: absolute;
-  top: 50%;
-  transform: translateY(-50%);
-  font-size: 2rem;
-  line-height: 1;
-  border-radius: 999px;
-  width: 44px;
-  height: 44px;
-}
-.control.nav.prev {
-  left: 12px;
-}
-.control.nav.next {
-  right: 12px;
-}
-.loading {
-  position: absolute;
-  bottom: 16px;
-  left: 50%;
-  transform: translateX(-50%);
-  margin: 0;
-  color: #d1d5db;
-}
 </style>
diff --git a/apps/viewer/src/components/album/AlbumHeader.vue b/apps/viewer/src/components/album/AlbumHeader.vue
index fd3bddf..bebbdcc 100644
--- a/apps/viewer/src/components/album/AlbumHeader.vue
+++ b/apps/viewer/src/components/album/AlbumHeader.vue
@@ -3,6 +3,7 @@ import { computed, onBeforeUnmount, ref, watch } from 'vue';
 import { useI18n } from 'vue-i18n';
 import { useRouter } from 'vue-router';
 import type { PublicAlbum, SortMode } from '../../api/client';
+import { copyText } from '../../support/clipboard';
 
 // UI-02 V02 活动信息区（从 ActivityPage 提取）：宣传图 + 标题/分享 + 说明 +
 // 元信息行（浏览/日期/地点）+ 排序/分类工具栏。数据与筛选决策仍在父级
@@ -130,31 +131,6 @@ const albumUrl = computed(() => {
   return new URL(path, window.location.origin).href;
 });
 
-async function copyText(text: string): Promise<boolean> {
-  try {
-    if (navigator.clipboard?.writeText !== undefined) {
-      await navigator.clipboard.writeText(text);
-      return true;
-    }
-  } catch {
-    // 走传统复制兜底
-  }
-  try {
-    const area = document.createElement('textarea');
-    area.value = text;
-    area.setAttribute('readonly', '');
-    area.style.position = 'fixed';
-    area.style.opacity = '0';
-    document.body.appendChild(area);
-    area.select();
-    const copied = document.execCommand('copy');
-    area.remove();
-    return copied;
-  } catch {
-    return false;
-  }
-}
-
 async function share(): Promise<void> {
   const copied = await copyText(albumUrl.value);
   shareState.value = copied ? 'copied' : 'failed';
diff --git a/apps/viewer/src/components/viewer/PhotoActionBar.vue b/apps/viewer/src/components/viewer/PhotoActionBar.vue
new file mode 100644
index 0000000..de0fa32
--- /dev/null
+++ b/apps/viewer/src/components/viewer/PhotoActionBar.vue
@@ -0,0 +1,305 @@
+<script setup lang="ts">
+import { computed, onBeforeUnmount, ref } from 'vue';
+import { useI18n } from 'vue-i18n';
+import type { DownloadVariant } from '../../api/client';
+
+// UI-02 §5.1/§5.4 底部操作栏（V04 新组件）：Like（coral 心形 + 累计数 +
+// 「连续点击」提示）/ Share / Download 三个均匀分布的大触控目标（≥44px）。
+// 下载关闭时整项移除，剩余按钮按 flex 均分自然重排；原图仅
+// canDownloadOriginal 时提供二级选项（长按主按钮或 ▾ 菜单：浏览图/原图）。
+// 本组件只发事件——点赞/分享/下载的业务编排在父级（PhotoLightbox）。
+
+const props = withDefaults(
+  defineProps<{
+    /** 当前照片展示计数（已含乐观 pending）。 */
+    likeCount: number;
+    /** 点赞动画 nonce（LikesController.popNonce）：变化即重挂心形重播心跳。 */
+    likePop?: number;
+    canDownload?: boolean;
+    canDownloadOriginal?: boolean;
+    /** 点赞提交中（预留：连续点赞不禁用，仅视觉态）。 */
+    isLiking?: boolean;
+  }>(),
+  { likePop: 0, canDownload: false, canDownloadOriginal: false, isLiking: false },
+);
+
+const emit = defineEmits<{
+  like: [];
+  share: [];
+  download: [variant: DownloadVariant];
+}>();
+
+const { t, locale } = useI18n();
+
+const likeCountText = computed(() => new Intl.NumberFormat(locale.value).format(props.likeCount));
+
+// —— 原图二级菜单：▾ 点击或主按钮长按（500ms）展开；点击直接下浏览图 ——
+
+const LONG_PRESS_MS = 500;
+
+const menuOpen = ref(false);
+let pressTimer: ReturnType<typeof setTimeout> | undefined;
+/** 长按已展开菜单：吞掉紧随的 click，避免长按判定又触发默认下载。 */
+let suppressClick = false;
+
+function startPress(): void {
+  if (!props.canDownloadOriginal) return;
+  pressTimer = setTimeout(() => {
+    menuOpen.value = true;
+    suppressClick = true;
+  }, LONG_PRESS_MS);
+}
+
+function cancelPress(): void {
+  if (pressTimer !== undefined) {
+    clearTimeout(pressTimer);
+    pressTimer = undefined;
+  }
+}
+
+function onDownloadClick(): void {
+  cancelPress();
+  if (suppressClick) {
+    suppressClick = false;
+    return;
+  }
+  menuOpen.value = false;
+  emit('download', 'browse');
+}
+
+function pickVariant(variant: DownloadVariant): void {
+  menuOpen.value = false;
+  emit('download', variant);
+}
+
+onBeforeUnmount(cancelPress);
+</script>
+
+<template>
+  <div class="action-bar">
+    <div class="action-slot like-slot">
+      <button
+        type="button"
+        class="action-btn"
+        :aria-label="t('viewer.like')"
+        @click="emit('like')"
+      >
+        <!-- :key 重挂触发心跳放大（沿用 Task 10 popNonce）；「减少动画」时禁用。 -->
+        <svg :key="likePop" class="action-icon like-icon" viewBox="0 0 24 24" aria-hidden="true" focusable="false">
+          <path d="M12 21.35l-1.45-1.32C5.4 15.36 2 12.28 2 8.5 2 5.42 4.42 3 7.5 3c1.74 0 3.41.81 4.5 2.09C13.09 3.81 14.76 3 16.5 3 19.58 3 22 5.42 22 8.5c0 3.78-3.4 6.86-8.55 11.54L12 21.35z" />
+        </svg>
+        <span class="like-count">{{ likeCountText }}</span>
+        <span class="action-label">{{ t('viewer.like') }}</span>
+      </button>
+      <!-- §5.1：Like 下方次级提示（12px），说明可连续点赞。 -->
+      <p class="like-hint">{{ t('viewer.tapMore') }}</p>
+    </div>
+
+    <div class="action-slot">
+      <button
+        type="button"
+        class="action-btn"
+        :aria-label="t('viewer.share')"
+        @click="emit('share')"
+      >
+        <svg class="action-icon" viewBox="0 0 24 24" aria-hidden="true" focusable="false">
+          <path d="M12 3v12" />
+          <path d="m7 8 5-5 5 5" />
+          <path d="M5 13v6a2 2 0 0 0 2 2h10a2 2 0 0 0 2-2v-6" />
+        </svg>
+        <span class="action-label">{{ t('viewer.share') }}</span>
+      </button>
+    </div>
+
+    <!-- 下载关闭时整项移除（不留可绕过直链）；剩余 slot flex 均分自动重排。 -->
+    <div v-if="canDownload" class="action-slot download-slot">
+      <div class="download-group">
+        <button
+          type="button"
+          class="action-btn download-main"
+          :aria-label="t('viewer.download')"
+          @click="onDownloadClick"
+          @pointerdown="startPress"
+          @pointerup="cancelPress"
+          @pointercancel="cancelPress"
+          @pointerleave="cancelPress"
+        >
+          <svg class="action-icon" viewBox="0 0 24 24" aria-hidden="true" focusable="false">
+            <path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4" />
+            <path d="m7 10 5 5 5-5" />
+            <path d="M12 15V3" />
+          </svg>
+          <span class="action-label">{{ t('viewer.download') }}</span>
+        </button>
+        <button
+          v-if="canDownloadOriginal"
+          type="button"
+          class="download-caret"
+          :aria-label="t('download.options')"
+          aria-haspopup="menu"
+          :aria-expanded="menuOpen"
+          @click="menuOpen = !menuOpen"
+        >
+          <svg viewBox="0 0 24 24" aria-hidden="true" focusable="false">
+            <path d="m6 9 6 6 6-6" />
+          </svg>
+        </button>
+        <div v-if="menuOpen && canDownloadOriginal" class="download-menu" role="menu" :aria-label="t('download.options')">
+          <button type="button" role="menuitem" @click="pickVariant('browse')">
+            {{ t('viewer.downloadBrowse') }}
+          </button>
+          <button type="button" role="menuitem" @click="pickVariant('original')">
+            {{ t('viewer.downloadOriginal') }}
+          </button>
+        </div>
+      </div>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+/* 深色底部操作栏（§5.1：约 88-104px + 安全区，安全区 padding 由父级 footer 承担）。
+ * token 经 .photo-viewer 链 var() 回退，独立挂载也成立。 */
+.action-bar {
+  display: flex;
+  align-items: stretch;
+  min-height: 88px;
+}
+.action-slot {
+  flex: 1 1 0;
+  min-width: 0;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+}
+.action-btn {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 2px;
+  min-width: var(--viewer-touch-target, 44px);
+  min-height: var(--viewer-touch-target, 44px);
+  border: none;
+  background: transparent;
+  color: #ffffff;
+  padding: 4px 12px;
+  cursor: pointer;
+}
+.action-btn:focus-visible {
+  outline: 2px solid var(--viewer-primary, #1a73e8);
+  border-radius: 8px;
+}
+.action-icon {
+  width: 24px;
+  height: 24px;
+  fill: none;
+  stroke: currentColor;
+  stroke-width: 1.8;
+  stroke-linecap: round;
+  stroke-linejoin: round;
+}
+/* Like：coral 实心心形 + 累计数（tabular-nums 稳定数字宽度）。 */
+.like-icon {
+  fill: var(--viewer-like-accent, #ff667d);
+  stroke: var(--viewer-like-accent, #ff667d);
+  animation: heart-pop 400ms ease-out;
+}
+@keyframes heart-pop {
+  0% {
+    transform: scale(1);
+  }
+  40% {
+    transform: scale(1.6);
+  }
+  100% {
+    transform: scale(1);
+  }
+}
+/* 「减少动画」：不心跳（数字仍即时跳动，§6.3）。 */
+:global(.viewer-reduced-motion) .like-icon {
+  animation: none;
+}
+.like-count {
+  font-variant-numeric: tabular-nums;
+  font-size: 1.0625rem;
+  font-weight: 700;
+  line-height: 1.2;
+}
+.like-hint {
+  margin: 2px 0 0;
+  max-width: 180px;
+  color: rgba(255, 255, 255, 0.55);
+  font-size: 12px;
+  line-height: 1.3;
+  text-align: center;
+}
+.action-label {
+  font-size: 0.8125rem;
+  color: rgba(255, 255, 255, 0.92);
+  line-height: 1.3;
+}
+/* —— 下载组：主按钮 + ▾；菜单向上弹出 —— */
+.download-group {
+  position: relative;
+  display: inline-flex;
+  align-items: center;
+}
+.download-caret {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  align-self: stretch;
+  min-width: 32px;
+  min-height: var(--viewer-touch-target, 44px);
+  border: none;
+  background: transparent;
+  color: rgba(255, 255, 255, 0.92);
+  cursor: pointer;
+}
+.download-caret:focus-visible {
+  outline: 2px solid var(--viewer-primary, #1a73e8);
+  border-radius: 6px;
+}
+.download-caret svg {
+  width: 20px;
+  height: 20px;
+  fill: none;
+  stroke: currentColor;
+  stroke-width: 2;
+  stroke-linecap: round;
+  stroke-linejoin: round;
+}
+.download-menu {
+  position: absolute;
+  bottom: calc(100% + 8px);
+  left: 50%;
+  transform: translateX(-50%);
+  z-index: 5;
+  display: grid;
+  min-width: 10em;
+  border: 1px solid rgba(255, 255, 255, 0.12);
+  border-radius: 10px;
+  background: rgba(22, 28, 36, 0.96);
+  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
+  padding: 4px;
+}
+.download-menu button {
+  min-height: var(--viewer-touch-target, 44px);
+  border: none;
+  border-radius: 6px;
+  background: transparent;
+  color: #ffffff;
+  padding: 0 14px;
+  text-align: left;
+  font-size: 0.9375rem;
+  cursor: pointer;
+}
+.download-menu button:hover {
+  background: rgba(255, 255, 255, 0.08);
+}
+.download-menu button:focus-visible {
+  outline: 2px solid var(--viewer-primary, #1a73e8);
+}
+</style>
diff --git a/apps/viewer/src/components/viewer/ThumbnailStrip.vue b/apps/viewer/src/components/viewer/ThumbnailStrip.vue
new file mode 100644
index 0000000..6ee5b59
--- /dev/null
+++ b/apps/viewer/src/components/viewer/ThumbnailStrip.vue
@@ -0,0 +1,184 @@
+<script setup lang="ts">
+import { computed, ref, watch } from 'vue';
+import { useI18n } from 'vue-i18n';
+import { reducedMotion } from '../../ui/prefs';
+
+// UI-02 §5.3 缩略图条（V04 新组件）：显示当前附近最多 7 项（手机约可见 5 项），
+// 当前项主色 2px 描边；点击切换 photoId（不新增浏览器历史——由父级导航入口
+// 统一走既有 replace 语义）。只消费已加载序列的临近窗口，不为填满条带加载
+// 整个相册；缩略图一律 thumb 变体 URL（不预载 browse 大图）。
+
+export interface ThumbnailItem {
+  photoId: string;
+  /** thumb 变体签名 URL；缺失时渲染占位块（保持条带高度稳定）。 */
+  thumbUrl?: string;
+  width?: number;
+  height?: number;
+}
+
+const props = defineProps<{
+  photos: ThumbnailItem[];
+  currentPhotoId: string | null;
+}>();
+
+const emit = defineEmits<{ select: [photoId: string] }>();
+
+const { t } = useI18n();
+
+/** 窗口半径：当前 ±3 → 最多 7 项；首尾自然收缩（不循环、不预取）。 */
+const WINDOW_RADIUS = 3;
+const WINDOW_MAX = WINDOW_RADIUS * 2 + 1;
+
+const currentIndex = computed(() => props.photos.findIndex((item) => item.photoId === props.currentPhotoId));
+
+const windowItems = computed(() => {
+  const total = props.photos.length;
+  if (total === 0) return [];
+  const anchor = currentIndex.value === -1 ? 0 : currentIndex.value;
+  const start = Math.max(0, Math.min(anchor - WINDOW_RADIUS, total - WINDOW_MAX));
+  const end = Math.min(total, start + WINDOW_MAX);
+  const result: { item: ThumbnailItem; index: number }[] = [];
+  for (let i = start; i < end; i += 1) result.push({ item: props.photos[i], index: i });
+  return result;
+});
+
+// —— 滚动编排：选中项滚入可见范围（遵守减少动画）；条带溢出提示 ——
+
+const trackEl = ref<HTMLElement | null>(null);
+const canScrollLeft = ref(false);
+const canScrollRight = ref(false);
+
+/** 减少动画判定：应用内偏好或系统 prefers-reduced-motion 任一命中即静止滚动。 */
+function prefersReducedMotion(): boolean {
+  if (reducedMotion.value) return true;
+  if (typeof window.matchMedia === 'function') {
+    return window.matchMedia('(prefers-reduced-motion: reduce)').matches;
+  }
+  return false;
+}
+
+function scrollCurrentIntoView(): void {
+  const track = trackEl.value;
+  if (track === null) return;
+  const current = track.querySelector<HTMLElement>('.thumb.current');
+  if (current === null) return;
+  if (typeof current.scrollIntoView !== 'function') return; // jsdom 无实现
+  current.scrollIntoView({
+    behavior: prefersReducedMotion() ? 'auto' : 'smooth',
+    block: 'nearest',
+    inline: 'center',
+  });
+}
+
+function updateOverflow(): void {
+  const el = trackEl.value;
+  if (el === null) {
+    canScrollLeft.value = false;
+    canScrollRight.value = false;
+    return;
+  }
+  canScrollLeft.value = el.scrollLeft > 1;
+  canScrollRight.value = el.scrollLeft + el.clientWidth < el.scrollWidth - 1;
+}
+
+watch(
+  [trackEl, () => props.currentPhotoId, () => props.photos] as const,
+  () => {
+    scrollCurrentIntoView();
+    updateOverflow();
+  },
+  { immediate: true, flush: 'post' },
+);
+</script>
+
+<template>
+  <nav class="thumb-strip" :aria-label="t('viewer.thumbnails')">
+    <div ref="trackEl" class="thumb-track" data-native-scroll @scroll.passive="updateOverflow">
+      <button
+        v-for="{ item, index } in windowItems"
+        :key="item.photoId"
+        type="button"
+        class="thumb"
+        :class="{ current: item.photoId === currentPhotoId }"
+        :aria-current="item.photoId === currentPhotoId ? 'true' : undefined"
+        :aria-label="t('viewer.thumbItem', { n: index + 1 })"
+        @click="emit('select', item.photoId)"
+      >
+        <img v-if="item.thumbUrl !== undefined" class="thumb-img" :src="item.thumbUrl" alt="" loading="lazy" draggable="false">
+        <span v-else class="thumb-placeholder" aria-hidden="true" />
+      </button>
+    </div>
+    <span v-if="canScrollLeft" class="thumb-fade left" aria-hidden="true" />
+    <span v-if="canScrollRight" class="thumb-fade right" aria-hidden="true" />
+  </nav>
+</template>
+
+<style scoped>
+/* 深色查看器内嵌条带：token 经 .photo-viewer 链 var() 回退，独立挂载也成立。 */
+.thumb-strip {
+  position: relative;
+  height: 56px;
+  flex: none;
+}
+.thumb-track {
+  display: flex;
+  gap: 6px;
+  align-items: center;
+  height: 100%;
+  overflow-x: auto;
+  scrollbar-width: none;
+  padding: 0 12px;
+  touch-action: pan-x;
+}
+.thumb-track::-webkit-scrollbar {
+  display: none;
+}
+/* §5.3：宽约 56-64px、高约 44-52px；非当前项保留透明 2px 边框防切换抖动。 */
+.thumb {
+  flex: none;
+  display: block;
+  width: 60px;
+  height: 48px;
+  padding: 0;
+  border: 2px solid transparent;
+  border-radius: var(--viewer-radius-img, 4px);
+  background: rgba(255, 255, 255, 0.08);
+  overflow: hidden;
+  cursor: pointer;
+}
+.thumb.current {
+  border-color: var(--viewer-primary, #1a73e8);
+}
+.thumb:focus-visible {
+  outline: 2px solid var(--viewer-primary, #1a73e8);
+  outline-offset: 1px;
+}
+.thumb-img {
+  display: block;
+  width: 100%;
+  height: 100%;
+  object-fit: cover;
+}
+.thumb-placeholder {
+  display: block;
+  width: 100%;
+  height: 100%;
+  background: rgba(255, 255, 255, 0.12);
+}
+/* 条带溢出提示：仅确有未滚出内容的一侧渐隐（不拦截指针）。 */
+.thumb-fade {
+  position: absolute;
+  top: 0;
+  bottom: 0;
+  width: 28px;
+  pointer-events: none;
+}
+.thumb-fade.right {
+  right: 0;
+  background: linear-gradient(to right, transparent, var(--viewer-dark-bg, #0e1218) 85%);
+}
+.thumb-fade.left {
+  left: 0;
+  background: linear-gradient(to left, transparent, var(--viewer-dark-bg, #0e1218) 85%);
+}
+</style>
diff --git a/apps/viewer/src/i18n/locales/en.ts b/apps/viewer/src/i18n/locales/en.ts
index 6e6446a..c1d07c6 100644
--- a/apps/viewer/src/i18n/locales/en.ts
+++ b/apps/viewer/src/i18n/locales/en.ts
@@ -79,6 +79,17 @@ export default {
     noPhotos: 'Photos coming soon',
     newPhotos: 'New photos',
     reduceMotion: 'Reduce motion',
+    // —— UI-02 (V04 dark immersive viewer) additions ——
+    photoViewer: 'Photo viewer',
+    photoPreview: 'Photo preview',
+    loadedCount: '{count} loaded',
+    tapMore: 'Tap to send more love',
+    download: 'Download',
+    downloadBrowse: 'Browse',
+    downloadOriginal: 'Original',
+    more: 'More options',
+    thumbnails: 'Thumbnail navigation',
+    thumbItem: 'Photo {n}',
   },
   route: { tokenLabel: 'Album token', photoLabel: 'Photo' },
   errors: {
diff --git a/apps/viewer/src/i18n/locales/zh-CN.ts b/apps/viewer/src/i18n/locales/zh-CN.ts
index 48d6f89..dbd27bd 100644
--- a/apps/viewer/src/i18n/locales/zh-CN.ts
+++ b/apps/viewer/src/i18n/locales/zh-CN.ts
@@ -79,6 +79,17 @@ export default {
     noPhotos: '照片即将上线',
     newPhotos: '有新照片',
     reduceMotion: '减少动画',
+    // —— UI-02（V04 深色大图查看器）新增 ——
+    photoViewer: '照片查看器',
+    photoPreview: '照片预览',
+    loadedCount: '已加载 {count} 张',
+    tapMore: '连续点击，为照片点赞',
+    download: '下载',
+    downloadBrowse: '浏览图',
+    downloadOriginal: '原图',
+    more: '更多选项',
+    thumbnails: '缩略图导航',
+    thumbItem: '第 {n} 张',
   },
   route: { tokenLabel: '相册令牌', photoLabel: '照片' },
   errors: {
diff --git a/apps/viewer/src/support/clipboard.ts b/apps/viewer/src/support/clipboard.ts
new file mode 100644
index 0000000..626a152
--- /dev/null
+++ b/apps/viewer/src/support/clipboard.ts
@@ -0,0 +1,28 @@
+// apps/viewer/src/support/clipboard.ts —— 剪贴板写入兜底（UI-02 V02 起
+// AlbumHeader 相册分享与 V04 大图 Share 共用）：优先 navigator.clipboard
+// （安全上下文），退回隐藏 textarea + execCommand('copy')（旧 WebView/
+// 非安全上下文）；均失败返回 false，由调用方展示可选中文本回退（§5.4）。
+export async function copyText(text: string): Promise<boolean> {
+  try {
+    if (navigator.clipboard?.writeText !== undefined) {
+      await navigator.clipboard.writeText(text);
+      return true;
+    }
+  } catch {
+    // 走传统复制兜底
+  }
+  try {
+    const area = document.createElement('textarea');
+    area.value = text;
+    area.setAttribute('readonly', '');
+    area.style.position = 'fixed';
+    area.style.opacity = '0';
+    document.body.appendChild(area);
+    area.select();
+    const copied = document.execCommand('copy');
+    area.remove();
+    return copied;
+  } catch {
+    return false;
+  }
+}
diff --git a/apps/viewer/src/viewer/position.ts b/apps/viewer/src/viewer/position.ts
new file mode 100644
index 0000000..d20a6a2
--- /dev/null
+++ b/apps/viewer/src/viewer/position.ts
@@ -0,0 +1,37 @@
+// apps/viewer/src/viewer/position.ts —— UI-02 §5.2 大图顶栏位置计数（纯数据层）。
+//
+// 数据诚实红线：不把已加载张数冒充相册总数、不为装饰计数新增 COUNT 查询。
+// 当前公开列表端点为游标分页（CursorPageMeta 只有 nextCursor/hasMore，无
+// total），因此「12 / 248」总分形态仅当接口将来提供准确 total 时出现——
+// 输入保留 total 字段，组件侧传 null 走真实回退：
+//   · 深链 solo 条目（自然位置未知）或尚未定位 → 「照片预览」，不伪造位置；
+//   · 有准确 total → 「i / total」；
+//   · 未到末页且无 total → 「已加载 N 张」；
+//   · 全部加载完成（!hasMore）且非 solo → 当前筛选序列「i / n」。
+// 文案拼接（i18n）在组件层完成；本模块只做形态判定，便于 vitest 直接覆盖。
+
+export interface PositionInput {
+  /** 当前照片在已加载序列中的下标；-1 = 尚未定位（渲染守卫后理论不出现，防御保留）。 */
+  index: number;
+  /** 已加载张数。 */
+  loaded: number;
+  /** 当前筛选范围的准确总数（API 提供）；无 → null（不得以 loaded 充当）。 */
+  total: number | null;
+  /** 序列是否已到末页（= !sequence.hasMore）。 */
+  atEnd: boolean;
+  /** 深链 solo 条目：追加在序列尾部兜底，自然位置未知。 */
+  solo: boolean;
+}
+
+export type PositionDisplay =
+  | { kind: 'preview' }
+  | { kind: 'total'; current: number; total: number }
+  | { kind: 'loaded'; count: number }
+  | { kind: 'index'; current: number; total: number };
+
+export function positionDisplay(input: PositionInput): PositionDisplay {
+  if (input.index < 0 || input.solo) return { kind: 'preview' };
+  if (input.total !== null) return { kind: 'total', current: input.index + 1, total: input.total };
+  if (!input.atEnd) return { kind: 'loaded', count: input.loaded };
+  return { kind: 'index', current: input.index + 1, total: input.loaded };
+}