[播放平滑修复]：完成可打断播报平滑播放，包含单输出流分块播放和TTS采样率保真

tests/test_transport.py

@@ -114,6 +114,24 @@ class TransportTests(unittest.TestCase):
 
         self.assertTrue(result.played)
         self.assertEqual(fake.output_writes, [b"\x00\x00\x01\x00"])
+        self.assertEqual(fake.output_stream_open_count, 1)
+
+    def test_sounddevice_chunk_playback_keeps_one_output_stream_open(self) -> None:
+        fake = FakeSoundDevice()
+        transport = SoundDeviceAudioTransport(sounddevice_module=fake)
+        segment = AudioSegment(b"\x00\x00" * 1600, 16000, 1, 0, 100)
+        callbacks: list[int] = []
+
+        result = transport.play_pcm_chunks(
+            segment,
+            chunk_ms=20,
+            after_chunk=lambda _chunk, elapsed_ms: callbacks.append(elapsed_ms) is not None and False,
+        )
+
+        self.assertTrue(result.played)
+        self.assertEqual(fake.output_stream_open_count, 1)
+        self.assertGreater(len(fake.output_writes), 1)
+        self.assertEqual(callbacks[-1], result.duration_ms)
 
     def test_sounddevice_device_report_uses_query_devices(self) -> None:
         fake = FakeSoundDevice()
@@ -162,6 +180,7 @@ class FakeSoundDevice:
     def __init__(self, callback_payloads: list[bytes] | None = None) -> None:
         self.callback_payloads = callback_payloads
         self.output_writes: list[bytes] = []
+        self.output_stream_open_count = 0
 
     def RawInputStream(self, **kwargs):
         if self.callback_payloads is not None:
@@ -169,6 +188,7 @@ class FakeSoundDevice:
         return FakeInputStream(**kwargs)
 
     def RawOutputStream(self, **kwargs):
+        self.output_stream_open_count += 1
         return FakeOutputStream(self, **kwargs)
 
     def query_devices(self):