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/schemas/event.py

@@ -4,7 +4,7 @@ from typing import Iterable, Optional, Dict, Any, List, Set, Callable
 from pydantic import BaseModel, Field, field_validator, model_validator
 
 from app.schemas.common import JsonData
-from app.schemas.message import MessageChannel
+from app.schemas.types import NotificationChannel
 from app.schemas.file import FileItem
 from app.schemas.media import OptionalMediaIdentityMixin, RequiredMediaIdentityMixin
 from app.schemas.types import MediaSource
@@ -366,7 +366,7 @@ class ResourceDownloadEventData(ChainEventData):
         # 输入参数
         context (Context): 当前资源上下文
         episodes (Set[int]): 需要下载的集数
-        channel (MessageChannel): 通知渠道
+        channel (NotificationChannel): 通知渠道
         origin (str): 来源（消息通知、Subscribe、Manual等）
         downloader (str): 下载器
         options (dict): 其他参数
@@ -380,7 +380,7 @@ class ResourceDownloadEventData(ChainEventData):
     # 输入参数
     context: Any = Field(None, description="当前资源上下文")
     episodes: Optional[Set[int]] = Field(None, description="需要下载的集数")
-    channel: Optional[MessageChannel] = Field(None, description="通知渠道")
+    channel: Optional[NotificationChannel] = Field(None, description="通知渠道")
     origin: Optional[str] = Field(None, description="来源")
     downloader: Optional[str] = Field(None, description="下载器")
     options: Optional[dict] = Field(default={}, description="其他参数")