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/workflow/actions/send_message.py

@@ -3,7 +3,7 @@ from typing import List, Optional, Union
 from pydantic import Field
 
 from app.workflow.actions import BaseAction, ActionChain
-from app.schemas import ActionParams, ActionContext, Notification
+from app.schemas import ActionParams, ActionContext, Message
 from app.runtime.config import settings
 
 
@@ -62,7 +62,7 @@ class SendMessageAction(BaseAction):
                 params.client = [""]
             for client in params.client:
                 ActionChain().post_message(
-                    Notification(
+                    Message(
                         source=client,
                         userid=params.userid,
                         title="【工作流执行结果】",