feat(player): 接入双端画中画播放

lib/pages/player/player_view.dart

@@ -200,6 +200,8 @@ class _PlayerPageState extends State<PlayerPage>
       );
     }
     _pageController = logic.pages;
+    // 自动小窗：独立播放页进入即挂；沉浸流随所在 tab 的激活状态挂/摘。
+    unawaited(logic.syncPipAutoArm(widget.embedded ? widget.active : true));
     if (!widget.embedded &&
         !logic.isEpisodeLocked(logic.session.currentEpisode)) {
       _loadingVisible = true;
@@ -217,6 +219,10 @@ class _PlayerPageState extends State<PlayerPage>
   void didUpdateWidget(covariant PlayerPage oldWidget) {
     super.didUpdateWidget(oldWidget);
     logic.attach(widget, isMounted: () => mounted);
+    // 沉浸流所在 tab 切换时同步自动小窗（激活挂、切走摘）。
+    if (widget.embedded && oldWidget.active != widget.active) {
+      unawaited(logic.syncPipAutoArm(widget.active));
+    }
     if (oldWidget.scrubCancelRequest != widget.scrubCancelRequest) {
       _cancelFeedScrub();
     }
@@ -703,6 +709,13 @@ class _PlayerPageState extends State<PlayerPage>
                 onRefresh: _refreshHomeFeed,
                 child: pages,
               );
+        // 进画中画时预加载当前集海报：还原过渡封面立即可显示，避免再黑一次。
+        if (logic.pip) {
+          final poster = logic.trackedEpisode?.posterUrl?.trim();
+          if (poster != null && poster.isNotEmpty) {
+            unawaited(precacheImage(NetworkImage(poster), context));
+          }
+        }
         return Stack(
           fit: StackFit.expand,
           clipBehavior: Clip.none,
@@ -711,7 +724,13 @@ class _PlayerPageState extends State<PlayerPage>
               pageController: _pageController,
               slots: _renderSlots(indices),
               onCurrentVideoVisible: _handleCurrentVideoVisible,
+              resumeSignal: logic.pipResumeToken,
             ),
+            if (logic.pipRecovering)
+              Positioned.fill(
+                key: const Key('player-pip-recover-cover'),
+                child: _PipRecoverCover(episode: logic.trackedEpisode),
+              ),
             if (!widget.embedded && !_loadingRemoved)
               Center(
                 child: IgnorePointer(
@@ -804,6 +823,9 @@ class _PlayerPageState extends State<PlayerPage>
 
   void _handleCurrentVideoVisible(int? index) {
     if (!mounted || _loadingRemoved) return;
+    // 收起还原封面要放在 early-return 之前：恢复时集未变，
+    // _videoReadyIndex 已相等，只有这里能接到淡入完成的回调。
+    logic.endPipRecover();
     final currentIndex = logic.session.currentIndex;
     if (index == null ||
         index != currentIndex ||
@@ -1447,3 +1469,43 @@ class _PlayerPageState extends State<PlayerPage>
     );
   }
 }
+
+/// 画中画还原过渡封面：盖住回前台瞬间的黑纹理帧，视频出帧后由
+/// [PlayerLogic.endPipRecover] 收起。背景用主题渐变，海报预加载命中前也有过渡观感。
+class _PipRecoverCover extends StatelessWidget {
+  const _PipRecoverCover({required this.episode});
+
+  final Episode? episode;
+
+  @override
+  Widget build(BuildContext context) {
+    final poster = episode?.posterUrl?.trim();
+    final thumbnail = episode?.thumbnailsUrl?.trim();
+    final url = poster != null && poster.isNotEmpty
+        ? poster
+        : (thumbnail != null && thumbnail.isNotEmpty ? thumbnail : null);
+    return DecoratedBox(
+      decoration: const BoxDecoration(
+        gradient: LinearGradient(
+          begin: Alignment.topCenter,
+          end: Alignment.bottomCenter,
+          colors: [
+            AppColors.followingGlow,
+            AppColors.followingGlowMid,
+            Color(0xFF101012),
+          ],
+          stops: [0, 0.22, 0.62],
+        ),
+      ),
+      child: url == null
+          ? const SizedBox.shrink()
+          : Image.network(
+              url,
+              key: const Key('player-pip-recover-cover-image'),
+              fit: BoxFit.cover,
+              gaplessPlayback: true,
+              errorBuilder: (_, _, _) => const SizedBox.shrink(),
+            ),
+    );
+  }
+}