fix(embed): pointer pause watchdog — capture does not cross iframe boundary, outside-release now auto-resumes in 2s

The earlier capture+window-listener fix is insufficient: releasing outside the 195x280 window dispatches pointerup in the host document, which no in-iframe listener can observe. Deterministic fallback: 2s watchdog on pointerdown force-clears the pause reason (in-frame releases still cancel it immediately).

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

apps/viewer/src/pages/embed/EmbedStream.vue

@@ -201,6 +201,9 @@ let pointerMoved = 0;
 let lockedTarget: string | null = null;
 /** 拖动抑制一次 click。 */
 let suppressClick = false;
+/** 按住看门狗（滚动卡死修复）：up 丢失（窗外释放）时 2s 强制恢复滚动。 */
+const POINTER_WATCHDOG_MS = 2000;
+let pointerWatchdog: ReturnType<typeof setTimeout> | null = null;
 let hoverPointerIsMouse = false;
 
 function scheduleResume(): void {
@@ -219,14 +222,22 @@ function onPointerDown(event: PointerEvent): void {
   const anchor = (event.target as HTMLElement).closest<HTMLElement>('a.stream-photo');
   lockedTarget = anchor === null ? null : (anchor.dataset.photoId ?? null);
   setReason('pointer', true);
-  // 指针捕获（滚动卡死修复 2026-09-23）：按下后拖出窗外松开时 viewport 收不到
-  // pointerup，'pointer' 暂停原因会永久残留 → 滚动停死。捕获后 up/cancel 必回
-  // 本元素；window 级兜底监听（onMounted）双保险。
+  // 指针捕获 + 看门狗（滚动卡死修复 2026-09-23）：按下后拖出窗外松开时，
+  // pointerup 发生在宿主文档——iframe 内任何监听都收不到（capture 不跨文档），
+  // 'pointer' 暂停原因会永久残留 → 滚动停死。看门狗 2s 强制恢复是确定性兜底；
+  // capture/window 监听让 iframe 内的释放更快恢复。
   try {
     viewportEl.value?.setPointerCapture(event.pointerId);
   } catch {
     /* 指针已释放等：忽略 */
   }
+  if (pointerWatchdog !== null) clearTimeout(pointerWatchdog);
+  pointerWatchdog = setTimeout(() => {
+    pointerWatchdog = null;
+    pointerDownY = null;
+    setReason('pointer', false);
+    scheduleResume();
+  }, POINTER_WATCHDOG_MS);
 }
 
 function onPointerMove(event: PointerEvent): void {
@@ -244,6 +255,10 @@ function onPointerMove(event: PointerEvent): void {
 
 function onPointerUp(): void {
   pointerDownY = null;
+  if (pointerWatchdog !== null) {
+    clearTimeout(pointerWatchdog);
+    pointerWatchdog = null;
+  }
   setReason('pointer', false);
   scheduleResume();
 }
@@ -373,6 +388,7 @@ onMounted(() => {
 
 onBeforeUnmount(() => {
   setReason('destroyed', true);
+  if (pointerWatchdog !== null) clearTimeout(pointerWatchdog);
   layerEl.value?.clear();
   document.removeEventListener('visibilitychange', onVisibilityChange);
   window.removeEventListener('pointerup', onWindowPointerEnd);