test(03-01): fix state recording test mock behavior

- Fix test_state_recording_failure to use correct mock pattern
- _try_official_subtitle returning None triggers _Whisper` fallback
- Ensure proper exception propagation for accurate failure recording

- All 22 tests passing

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_processors/test_asr.py

@@ -575,7 +575,8 @@ class TestStateRecording:
             processor = ASRProcessor(state_manager=mock_state_manager)
             mock_state_manager.load.return_value = mock_state
 
-            with patch.object(processor, "_try_official_subtitle", side_effect=Exception("Network error")):
+            # _try_official_subtitle 返回 None（无字幕）
+            with patch.object(processor, "_try_official_subtitle", return_value=None):
                 with patch.object(processor, "_run_whisper", side_effect=Exception("Whisper error")):
                     input_data = ASRInput(
                         content_id="BV1xx",
@@ -583,7 +584,7 @@ class TestStateRecording:
                         video_path=str(video_path)
                     )
 
-                    with pytest.raises(Exception):
+                    with pytest.raises(Exception, match="Whisper error"):
                         await processor.process(input_data)
 
                     # 应该调用 mark_step_failed