fix(playback): harden offline source reporting

lib/services/playback_progress_tracker.dart

@@ -74,6 +74,8 @@ class PlaybackProgressTracker {
   /// Whether the final stopped progress event was already emitted locally.
   bool _stopProgressNotified = false;
 
+  Future<void>? _stoppedProgressFuture;
+
   Duration? _lastProgressNotifiedPosition;
 
   static const Duration _progressNotifyDelta = Duration(seconds: 30);
@@ -162,6 +164,20 @@ class PlaybackProgressTracker {
     await _sendProgress(state, positionOverride: positionOverride);
   }
 
+  Future<void> sendStoppedProgressOnce({Duration? positionOverride}) {
+    final existing = _stoppedProgressFuture;
+    if (existing != null) return existing;
+    final future = sendProgress('stopped', positionOverride: positionOverride);
+    _stoppedProgressFuture = future;
+    return future;
+  }
+
+  void resumeAfterStoppedReport() {
+    _stoppedProgressFuture = null;
+    _stopProgressNotified = false;
+    _reportSession?.resetAfterStop();
+  }
+
   Future<void> _sendProgress(String state, {Duration? positionOverride}) async {
     Duration? attemptedPosition;
     Duration? attemptedDuration;