fix audio cutoff: don't Stop() after playback, let NAudio drain naturally

Robovoice.App/VoicePipeline.cs

@@ -68,9 +68,6 @@ internal sealed class VoicePipeline : IDisposable
         _currentSession++;
         _gate.Reset();
         _audioOutput.Stop();
-
-        // Unblock player thread if it's waiting on audioQueue.Take()
-        _audioQueue.Add(new AudioItem(_currentSession - 1, null));
     }
 
     public void OnPttReleased()
@@ -122,20 +119,21 @@ internal sealed class VoicePipeline : IDisposable
             _gate.Wait();
             if (!_running) break;
 
-            // Block until first audio item is available
-            AudioItem firstItem;
-            try
-            {
-                firstItem = _audioQueue.Take();
-            }
-            catch (InvalidOperationException)
+            // Drain stale items, then wait for real audio for current session
+            AudioItem firstItem = default!;
+            while (_running)
             {
+                try { firstItem = _audioQueue.Take(); }
+                catch (InvalidOperationException) { return; }
+
+                if (firstItem.Session != _currentSession)
+                    continue;
+
                 break;
             }
 
             if (!_running) break;
-            if (firstItem.Session != _currentSession)
-                continue;
+
             if (firstItem.Samples == null)
             {
                 // :F with no audio — nothing to play
@@ -161,7 +159,6 @@ internal sealed class VoicePipeline : IDisposable
             }
 
             _audioOutput.Flush();
-            _audioOutput.Stop();
             _log("TTS: playback finished");
             _gate.Reset();
         }