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

tests/test_agent_session_status.py

@@ -10,7 +10,7 @@ from langchain_core.messages import AIMessage
 from app.agent.middleware.usage import UsageMiddleware
 from app.agent import AgentManager
 from app.chain.message import MessageChain
-from app.schemas.types import MessageChannel
+from app.schemas.types import NotificationChannel
 
 
 class TestAgentSessionStatus(unittest.TestCase):
@@ -100,7 +100,7 @@ class TestAgentSessionStatus(unittest.TestCase):
             patch.object(chain, "post_message") as post_message,
         ):
             chain.remote_session_status(
-                channel=MessageChannel.Telegram,
+                channel=NotificationChannel.Telegram,
                 userid="10001",
                 source="telegram-test",
             )
@@ -121,7 +121,7 @@ class TestAgentSessionStatus(unittest.TestCase):
 
         with patch.object(chain, "post_message") as post_message:
             chain.remote_session_status(
-                channel=MessageChannel.Telegram,
+                channel=NotificationChannel.Telegram,
                 userid="10001",
                 source="telegram-test",
             )