Task 15: product detail anchor tabs + per-product custom sections

User report: product detail page was wrong — section titles are
per-product custom data (CMS wppop_sections migration: Packing &
Delivery / Our Exhibition / Our Certifications / Our Company / FAQ),
not fixed headings; they must drive an anchor tab system like the
CMS [locale]/products/[slug].astro detailTabs.

Data side (both layers, task option 1 + 2):

- theme_pro.product_detail_sections: fields.sections
  [{title, content}] JSON is the structured source; legacy sync
  output that appended sections as trailing body H2 blocks is
  recognized by known/data titles and split out (overview keeps the
  rest; same-title blocks dedupe to the structured version; Features
  body block drops when fields.features renders it)
- sync_cms_data.build_product: store sections/features as structured
  fields JSON, stop appending H2 blocks to the body; stats now count
  entries with a sections field
- Specifications table no longer leaks structural JSON field keys
  (sections/features/specs/gallery/categories) — scalar spec keys
  only

Template side (trade-pro product.html, replaces 12a panel
switching):

- tab sequence is fully data-driven and matches the CMS: Product
  Details (always) -> custom sections (data titles) ->
  Specifications / Features (shown only when data exists)
- tabs are #anchor links, not panel toggles: all sections render
  flat with visible titles (readable and crawlable without JS; native
  anchor jump), JS adds smooth scrolling + scrollspy highlight +
  tab centering in the horizontal scroll row
- section ids are slug-derived (sec-packing-delivery), duplicate
  titles get an index suffix; features grid ports the CMS
  detail-feature-row

Tests: test_trade_pro_product_layout_structure rewritten for the
anchor-tab contract — sections via fields, legacy body-H2 fallback,
spec/features conditional tabs, no-sections product showing only
Product Details + Specifications, spec table free of JSON key leaks,
updated pro.css needles. 30 passed; the 1 failure
(test_trade_pro_blocks_visual_bridge) fails identically on the
previous commit (pre-existing, unrelated).

Co-Authored-By: Claude Code <noreply@example.com>

themes/trade-pro/pro.css

@@ -104,8 +104,9 @@
 .sf-theme-trade-pro .sf-tp-cta h2{margin-block-end:var(--sf-tp-space-2);color:var(--sf-tp-color-text-inverse)}
 .sf-theme-trade-pro .sf-tp-cta p{color:color-mix(in srgb,var(--sf-tp-color-text-inverse) 83%,transparent);margin:0}
 
-/* ── 产品详情（Task 12a，[slug].astro 精确对齐重做 10b）：hero 画廊/标题 +
-   sticky 选项卡（无 JS 平铺回退）+ rich-body 正文表格 + spec-table + 询盘。
+/* ── 产品详情（Task 12a，[slug].astro 精确对齐重做 10b；Task 15 选项卡改
+   锚点 Tab + 自定义区块/特性栅格）：hero 画廊/标题 + sticky 锚点选项卡 +
+   rich-body 正文表格 + spec-table + detail-features + 询盘。
    断点映射：cms 900 与 960（询盘堆叠）→ 900；cms 620 → 620。 ── */
 .sf-theme-trade-pro .sf-tp-product-hero{padding-block:calc(var(--sf-tp-space-8) + var(--sf-tp-space-4)) var(--sf-tp-space-8)}
 .sf-theme-trade-pro .sf-tp-breadcrumb{display:flex;flex-wrap:wrap;align-items:center;color:var(--sf-tp-color-text-muted);font-size:var(--sf-tp-font-size-sm);margin-block-end:var(--sf-tp-space-6)}
@@ -137,13 +138,13 @@
 /* Tab 单行横滚（数量多不换行）；隐藏滚动条 + scroll-snap 贴合（cms .tabs-row） */
 .sf-theme-trade-pro .sf-tp-tabs-row{display:flex;gap:var(--sf-tp-space-6);overflow-x:auto;scroll-behavior:smooth;scrollbar-width:none;scroll-snap-type:x proximity}
 .sf-theme-trade-pro .sf-tp-tabs-row::-webkit-scrollbar{display:none}
-.sf-theme-trade-pro .sf-tp-tab{flex:0 0 auto;white-space:nowrap;padding:var(--sf-tp-space-4) var(--sf-tp-space-1);color:var(--sf-tp-color-text-secondary);font-weight:var(--sf-tp-font-weight-semibold);font-size:var(--sf-tp-font-size-sm);background:none;border:none;border-block-end:var(--sf-tp-border-width-strong) solid transparent;cursor:pointer;scroll-snap-align:center}
+.sf-theme-trade-pro .sf-tp-tab{flex:0 0 auto;white-space:nowrap;padding:var(--sf-tp-space-4) var(--sf-tp-space-1);color:var(--sf-tp-color-text-secondary);font-weight:var(--sf-tp-font-weight-semibold);font-size:var(--sf-tp-font-size-sm);background:none;border:none;border-block-end:var(--sf-tp-border-width-strong) solid transparent;cursor:pointer;scroll-snap-align:center;text-decoration:none}
 .sf-theme-trade-pro .sf-tp-tab.active,.sf-theme-trade-pro .sf-tp-tab:hover{color:var(--sf-tp-color-text-link);border-block-end-color:var(--sf-tp-color-border-brand)}
-/* 面板切换（cms [data-tabbed].tabs-enabled）：JS 给容器加 sf-tp-tabs-enabled 后
-   仅显示激活面板并隐藏 panel-title；无 JS 时面板全部平铺可读、标题可见 */
-.sf-theme-trade-pro .sf-tp-product-tabbed.sf-tp-tabs-enabled .sf-tp-panel{display:none}
-.sf-theme-trade-pro .sf-tp-product-tabbed.sf-tp-tabs-enabled .sf-tp-panel.active{display:block}
-.sf-theme-trade-pro .sf-tp-product-tabbed.sf-tp-tabs-enabled .sf-tp-panel-title{display:none}
+.sf-theme-trade-pro .sf-tp-tab:focus-visible{outline:2px solid var(--sf-tp-color-border-brand);outline-offset:-2px}
+/* 锚点选项卡（Task 15 重做 12a 面板切换）：Tab 是页内锚点链接，区块全部平铺
+   渲染、panel-title 常显（无 JS 原生跳转也可读）；JS 平滑滚动 + scrollspy
+   高亮当前 Tab（.sf-tp-tab.active）。区块锚点滚动让位 sticky 条见下方
+   .sf-tp-detail-section 的 scroll-margin-top。 */
 /* 详情面板（cms .detail-section）：区块距 + 锚点滚动让位 sticky 选项卡；
    区块标题品牌色 3px 下划短线（cms .detail-section > .wrap > h2） */
 .sf-theme-trade-pro .sf-tp-detail-section{padding-block:calc(var(--sf-tp-space-10) + var(--sf-tp-space-1));scroll-margin-top:calc(var(--sf-tp-space-16) + var(--sf-tp-space-16))}
@@ -165,6 +166,13 @@
 .sf-theme-trade-pro .sf-tp-spec-table{width:100%;border-collapse:collapse;font-size:var(--sf-tp-font-size-sm)}
 .sf-theme-trade-pro .sf-tp-spec-table th,.sf-theme-trade-pro .sf-tp-spec-table td{border:var(--sf-tp-border-width-hairline) solid var(--sf-tp-color-border-default);padding:calc(var(--sf-tp-space-4) - var(--sf-tp-space-1)) var(--sf-tp-space-4);text-align:start}
 .sf-theme-trade-pro .sf-tp-spec-table th{background:var(--sf-tp-color-surface-muted);font-weight:var(--sf-tp-font-weight-semibold)}
+/* 特性栅格（cms .detail-feature-row，fields.features 数据驱动）：品牌色星标 +
+   标题/描述两行卡；auto-fit 自适应条目数（cms 固定 4 列，数据条目不定） */
+.sf-theme-trade-pro .sf-tp-detail-features{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:var(--sf-tp-space-3) var(--sf-tp-space-6)}
+.sf-theme-trade-pro .sf-tp-detail-feature{display:grid;grid-template-columns:auto 1fr;gap:var(--sf-tp-space-3);align-items:start;padding-block:var(--sf-tp-space-2)}
+.sf-theme-trade-pro .sf-tp-detail-feature>span{color:var(--sf-tp-color-text-brand);font-size:var(--sf-tp-font-size-xl);line-height:var(--sf-tp-line-height-tight)}
+.sf-theme-trade-pro .sf-tp-detail-feature h3{font-size:var(--sf-tp-font-size-md);margin-block-end:var(--sf-tp-space-1)}
+.sf-theme-trade-pro .sf-tp-detail-feature p{margin:0;color:var(--sf-tp-color-text-muted);font-size:var(--sf-tp-font-size-sm)}
 /* 询盘板块（cms quote-grid 同构）：左联系信息 + 右表单卡 */
 .sf-theme-trade-pro .sf-tp-quote-grid{display:grid;grid-template-columns:0.85fr 1.15fr;gap:calc(var(--sf-tp-space-12) + var(--sf-tp-space-4));align-items:start}
 .sf-theme-trade-pro .sf-tp-quote-info>p{color:var(--sf-tp-color-text-muted)}