fix: 修复 coordinator.py 导入错误

问题：MeshMessageEvent 和 ProvDeviceEvent 定义在 serial_reader.py
但 coordinator.py 错误地从 protocol_parser.py 导入

修复：
- 从 protocol_parser 导入移除这两个类
- 改为从 serial_reader 导入
- 移除 _setup_callbacks 中多余的内部导入

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

custom_components/sigmesh_gateway/coordinator.py

@@ -14,12 +14,14 @@ from .const import DOMAIN
 from .protocol_parser import (
     DeviceManager,
     DeviceState,
-    MeshMessageEvent,
     ParsedMeshMessage,
-    ProvDeviceEvent,
     ProtocolParser,
 )
-from .serial_reader import SerialReader
+from .serial_reader import (
+    MeshMessageEvent,
+    ProvDeviceEvent,
+    SerialReader,
+)
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -57,12 +59,6 @@ class SigMeshGatewayCoordinator(DataUpdateCoordinator[dict[str, DeviceState]]):
 
     def _setup_callbacks(self) -> None:
         """设置串口读取器的回调函数."""
-        from .serial_reader import (
-            MeshMessageEvent,
-            ProvDeviceEvent,
-            SerialDataEvent,
-        )
-
         def on_mesh_message_handler(event: MeshMessageEvent) -> None:
             """处理 Mesh 消息回调."""
             self.hass.async_create_task(self._handle_mesh_message(event))