[唤醒应答与快速端点]：完成唤醒后我在播报和本地VAD端点优化，包含缓冲清理、配置项和测试覆盖

tests/test_live_runtime.py

@@ -80,7 +80,7 @@ def make_runtime(texts: list[str], context: ConversationContext | None = None) -
     tts = SineTtsProvider()
     reporter = RecordingReporter()
     runtime = LiveVoiceRuntime(
-        config=AppConfig(llm_api_key="secret", speech_provider="cloud"),
+        config=AppConfig(llm_api_key="secret", speech_provider="cloud", post_playback_drain_ms=0),
         transport=transport,
         wakeword=KeywordWakeWordProvider(),
         vad_recorder=VadRecorder(EnergyVadProvider(), min_duration_ms=40, end_silence_ms=40),
@@ -101,8 +101,9 @@ class LiveRuntimeTests(unittest.TestCase):
         self.assertEqual(summary.completed_turns, 2)
         self.assertEqual(len(stt.calls), 2)
         self.assertEqual(len(llm.calls), 2)
-        self.assertEqual(len(transport.played_segments), 2)
+        self.assertEqual(len(transport.played_segments), 4)
         self.assertEqual(reporter.transcripts, ["第一问", "第二问"])
+        self.assertIn("应答中：我在", reporter.statuses)
         self.assertIn("恢复待机：可继续唤醒", reporter.statuses[-1])
 
     def test_temporary_context_is_sent_to_second_llm_call(self) -> None: