fix(audio): guard underrun/stream-complete against false end-of-playback

pause() clears underrun_ so setStreamComplete can't fire TrackEnded while paused; resetToStart() resets streamComplete. Prior fix: underrun_ park + streamComplete discriminator prevent the Opus-startup false-end. Tests: 18 PlaybackScheduler cases including pause-during-underrun and underrun->resume->genuine-end-once.

DeepDrftPublic/Interop/audio/AudioPlayer.ts

@@ -237,6 +237,12 @@ export class AudioPlayer {
                 }
             }
             this.streamingCompleted = true;
+            // Hand the genuine-end signal to the scheduler AFTER the tail buffers are added and
+            // scheduled: now an empty scheduled queue is a real end-of-track, not a startup gap, so
+            // the scheduler may fire onPlaybackEnded when its queue drains. If the queue was already
+            // empty at this point (the tail produced no buffers, or they were already played),
+            // setStreamComplete finalises immediately.
+            this.scheduler.setStreamComplete(true);
             return { success: true, bufferCount: this.scheduler.getBufferCount() };
         } catch (error) {
             return { success: false, error: (error as Error).message };
@@ -321,9 +327,13 @@ export class AudioPlayer {
                 }
             }
 
-            // Check if streaming is complete
+            // Check if streaming is complete. The StreamDecoder self-detects completion by byte
+            // count (WAV/MP3/FLAC); propagate that to the scheduler so a drained queue past this
+            // point is treated as a genuine end. Buffers from this chunk were already added above,
+            // so any final end fires through handleSourceEnded when they drain.
             if (this.streamDecoder.isComplete) {
                 this.streamingCompleted = true;
+                this.scheduler.setStreamComplete(true);
             }
 
             const canStart = this.streamDecoder.headerParsed &&