Clear stale ASR capture on end of utterance in DuplexPipeline. Add test to verify behavior when conversation state changes, ensuring proper handling of ASR capture variables.

engine/core/duplex_pipeline.py

@@ -1393,6 +1393,11 @@ class DuplexPipeline:
     async def _on_end_of_utterance(self) -> None:
         """Handle end of user utterance."""
         if self.conversation.state not in (ConversationState.LISTENING, ConversationState.INTERRUPTED):
+            # Prevent a stale ASR capture watchdog from repeatedly forcing EOU
+            # once the conversation has already moved past user-listening states.
+            self._asr_capture_active = False
+            self._asr_capture_started_ms = 0.0
+            self._pending_speech_audio = b""
             return
 
         # Add a tiny trailing silence tail to stabilize final-token decoding.