Fix Potential state duplication on barge-in.

core/duplex_pipeline.py

@@ -659,7 +659,9 @@ class DuplexPipeline:
         if self.llm_service and hasattr(self.llm_service, 'cancel'):
             self.llm_service.cancel()
         
-        # Interrupt conversation
+        # Interrupt conversation only if there is no active turn task.
+        # When a turn task exists, it will handle end_assistant_turn() to avoid double callbacks.
+        if not (self._current_turn_task and not self._current_turn_task.done()):
             await self.conversation.interrupt()
         
         # Reset for new user turn