[Pipeline 事件总线]：完成语音助手事件模型，包含stage事件、终端reporter和测试覆盖

src/owner_voice_pet/__init__.py

@@ -1,6 +1,7 @@
 """Owner voice pet pipeline package."""
 
 from .config import AppConfig
+from .events import PipelineEvent, PipelineEventBus
 from .models import (
     AudioFrame,
     AudioSegment,
@@ -29,6 +30,8 @@ from .ui import ConsolePetWindow, PetStateController, PetVisualState
 
 __all__ = [
     "AppConfig",
+    "PipelineEvent",
+    "PipelineEventBus",
     "AudioFrame",
     "AudioSegment",
     "AudioRingBuffer",