fix(queue): guard OnTrackEnded against direct-play cross-context advance

Only advance when player's CurrentTrack.Id matches queue's Current.Id;
direct-play call sites (SessionDetail, StreamNowButton, resume) that
supersede the queue no longer spuriously advance the album. Adds
regression test covering the scenario.

DeepDrftPublic.Client/Services/QueueService.cs

@@ -108,9 +108,17 @@ public sealed class QueueService : IQueueService, IDisposable
     // Advance on organic end-of-stream only. TrackEnded is not raised by stop/unload/track-switch,
     // so a manual stop or a fresh single-track selection elsewhere never spuriously advances the
     // queue. When the queue is past its last track, end-of-stream simply stops — nothing to advance.
+    //
+    // Guard: only advance when the track that just ended is the queue's own current item. Call sites
+    // that stream a single track directly (SessionDetail, StreamNowButton, resume from AudioPlayerBar)
+    // overwrite the player's CurrentTrack without touching the queue. If their track reaches natural
+    // end, the player fires TrackEnded — but the queue's Current no longer matches the player's
+    // CurrentTrack, so we must not advance. Id-based equality is used rather than ReferenceEquals
+    // because DTO copies through serialisation are not reference-equal.
     private void OnTrackEnded()
     {
         if (!HasNext) return;
+        if (_player?.CurrentTrack?.Id != Current?.Id) return;
         // Fire-and-forget is deliberate: TrackEnded is a synchronous event invoked from the player's
         // end-of-playback callback continuation; we must not block it. Advancing kicks off the next
         // stream, whose own failures surface through the player's ErrorMessage/state — the queue does