fix(playback): keep Plex playlist queue when entering the player

close #978

lib/providers/playback_state_provider.dart

@@ -67,6 +67,15 @@ class PlaybackStateProvider with ChangeNotifier, DisposableChangeNotifierMixin {
   /// Whether any queue-based playback is active
   bool get isQueueActive => _playQueueId != null && _isQueueMode;
 
+  /// Whether [item] belongs to the currently active queue. True for Plex
+  /// items the server-side queue stamped with a `playQueueItemId`, and for
+  /// items present in a Jellyfin local queue (synthetic id). Gates the
+  /// player's "preserve vs. wipe launcher-set queue" decision in both
+  /// [VideoPlayerScreen.initState] and `_ensurePlayQueue`, so a playlist
+  /// or collection queue survives entry into the player instead of being
+  /// replaced with a show queue.
+  bool isItemInActiveQueue(MediaItem item) => isQueueActive && playQueueItemIdFor(item) != null;
+
   /// The context key (show/season/playlist ratingKey) for the current session
   String? get shuffleContextKey => _contextKey;
 

lib/screens/video_player/parts/episode_queue.dart

@@ -34,20 +34,19 @@ extension _VideoPlayerEpisodeQueueMethods on VideoPlayerScreenState {
         return;
       }
 
-      // Check if there's already an active queue for THIS show.
-      // A leftover queue from a different show or — more importantly —
-      // from a different backend (Jellyfin's local queue is published
-      // here too) would otherwise mask the new show's navigation.
-      final existingContextKey = playbackState.shuffleContextKey;
-      final isQueueActive = playbackState.isQueueActive;
-
-      if (isQueueActive && existingContextKey == showRatingKey) {
+      // Preserve any queue this item belongs to — playlist, collection,
+      // or same-show queue. `isItemInActiveQueue` is the same gate
+      // VideoPlayerScreen.initState uses; a context-key check alone would
+      // wipe a playlist queue (its key is the playlist id, not the show).
+      // Only when the active queue is genuinely stale (item not in it)
+      // do we clobber and create a fresh show queue.
+      if (playbackState.isItemInActiveQueue(_currentMetadata)) {
         playbackState.setCurrentItem(_currentMetadata);
-        appLogger.d('Using existing play queue (context: $existingContextKey)');
+        appLogger.d('Using existing play queue (context: ${playbackState.shuffleContextKey})');
         return;
       }
-      if (isQueueActive) {
-        appLogger.d('Resetting stale play queue (was: $existingContextKey, now: $showRatingKey)');
+      if (playbackState.isQueueActive) {
+        appLogger.d('Resetting stale play queue (was: ${playbackState.shuffleContextKey}, now: $showRatingKey)');
         playbackState.clearShuffle();
       }
 

lib/screens/video_player_screen.dart

@@ -449,8 +449,7 @@ class VideoPlayerScreenState extends State<VideoPlayerScreen> with WidgetsBindin
         // playback (continue-watching, direct episode tap with no queue
         // launcher) clear any stale queue so prev/next stays consistent.
         final meta = widget.metadata;
-        final inActiveQueue = playbackState.isQueueActive && playbackState.playQueueItemIdFor(meta) != null;
-        if (inActiveQueue) {
+        if (playbackState.isItemInActiveQueue(meta)) {
           playbackState.setCurrentItem(meta);
         } else {
           playbackState.clearShuffle();