fix: assign seek CTS synchronously and guard load finally to stop seek/load race

DeepDrftPublic.Client/Services/StreamingAudioPlayerService.cs

@@ -184,9 +184,14 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
         finally
         {
             IsLoading = false;
+            // Only notify if this load is still the active operation. A superseding seek
+            // owns state notifications; firing here mid-seek would push a stale snapshot.
+            if (ReferenceEquals(_streamingCancellation, loadCts))
+            {
                 await NotifyStateChanged();
             }
         }
+    }
 
     /// <summary>
     /// Fetches and decodes the track's waveform loudness profile, then notifies state so the
@@ -442,11 +447,21 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
         // OperationCanceledException asynchronously; if we kick off a new loop
         // immediately, both can race against the single-instance JS StreamDecoder
         // and corrupt decode state. Draining here is the load-bearing guarantee.
-        _streamingCancellation?.Cancel();
+        //
-        await DrainActiveStreamingTaskAsync();
+        // Invariant: any caller that supersedes a load WITHOUT wanting the load's
-        _streamingCancellation?.Dispose();
+        // state reset must assign its own CTS to _streamingCancellation *before*
+        // its first await. LoadTrackStreaming's OCE continuation fires during the
+        // drain await on the shared _activeStreamingTask; it resets IsLoaded/
+        // IsStreamingMode only when _streamingCancellation still equals its loadCts.
+        // Assigning seekCts synchronously here makes that identity check fail, so
+        // the seek's state survives. (ResetToIdle deliberately does NOT do this —
+        // it wants the reset, and nulls _streamingCancellation only after the drain.)
+        var oldCts = _streamingCancellation;
         var seekCts = new CancellationTokenSource();
         _streamingCancellation = seekCts;
+        oldCts?.Cancel();
+        await DrainActiveStreamingTaskAsync();
+        oldCts?.Dispose();
 
         try
         {