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/prompt/__init__.py

@@ -15,7 +15,7 @@ from app.runtime.log import logger
 from app.schemas import (
     ChannelCapability,
     ChannelCapabilities,
-    MessageChannel,
+    NotificationChannel,
     ChannelCapabilityManager,
 )
 from app.adapters.system.host import SystemUtils
@@ -128,7 +128,7 @@ class PromptManager:
         markdown_spec = ""
         msg_channel = (
             next(
-                (c for c in MessageChannel if c.value.lower() == channel.lower()), None
+                (c for c in NotificationChannel if c.value.lower() == channel.lower()), None
             )
             if channel
             else None
@@ -356,7 +356,7 @@ class PromptManager:
 
     @staticmethod
     def _generate_button_choice_instructions(
-        channel: MessageChannel = None,
+        channel: NotificationChannel = None,
     ) -> str:
         if (
             channel