Fix Race risks if process_audio is called concurrently.

core/duplex_pipeline.py

@@ -111,6 +111,7 @@ class DuplexPipeline:
         max_buffer_seconds = settings.max_audio_buffer_seconds if hasattr(settings, "max_audio_buffer_seconds") else 30
         self._max_audio_buffer_bytes = int(settings.sample_rate * 2 * max_buffer_seconds)
         self._last_vad_status: str = "Silence"
+        self._process_lock = asyncio.Lock()
         
         # Interruption handling
         self._interrupt_event = asyncio.Event()
@@ -208,6 +209,7 @@ class DuplexPipeline:
             return
         
         try:
+            async with self._process_lock:
                 # 1. Process through VAD
                 vad_result = self.vad_processor.process(pcm_bytes, settings.chunk_size_ms)