refactor(schemas): 统一 message/notification 命名边界，旧名收敛至兼容映射表

- notification 域：渠道能力（MessageChannel→NotificationChannel、ChannelCapability* 迁入 notification.py）
- message 域：消息收发（Notification→Message、NotificationType→MessageType、CommingMessage→IncomingMessage、NotificationHistoryItem→MessageHistoryItem、NotificationClear*→MessageClear*）
- Agent 工具契约：send_notification_message→send_message、notification_callback→message_callback
- 源码不保留旧名物理别名，旧导入经 app/runtime/compat/manifest.py SYMBOL_ALIASES 惰性解析
- API 路径与持久化键冻结不变，前端零改动
- 新增兼容守护测试与 docs/rules/07 命名边界规范

app/agent/tools/impl/run_slash_command.py

@@ -9,7 +9,7 @@ from app.agent.tools.base import MoviePilotTool
 from app.agent.tools.tags import ToolTag
 from app.runtime.events import eventmanager
 from app.runtime.log import logger
-from app.schemas.types import EventType, MessageChannel
+from app.schemas.types import EventType, NotificationChannel
 
 
 class RunSlashCommandInput(BaseModel):
@@ -83,7 +83,7 @@ class RunSlashCommandTool(MoviePilotTool):
             channel = None
             if self._channel:
                 try:
-                    channel = MessageChannel(self._channel)
+                    channel = NotificationChannel(self._channel)
                 except (ValueError, KeyError):
                     channel = None