feat: 增强 Agent 意图识别和上下文管理

- 新增 intent_router.py 意图路由模块
- 优化 context.py 上下文管理
- 增强 loop.py Agent 运行循环
- 更新 memory.py 记忆模块
- 修复 builtin.py 工具函数

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/agents/tools/builtin.py

@@ -275,7 +275,7 @@ class WebSearchTool(Tool):
 
     @property
     def description(self) -> str:
-        return "Search the web for information using a search engine."
+        return "Search the web for current information, real-time data, or information that is not in your training data. **Only use this when the user explicitly asks for** latest news, current events, real-time information, or specifically requests a web search. **DO NOT use for simple questions** like '介绍一下武汉', '什么是AI' - answer from your knowledge instead."
 
     @property
     def parameters(self) -> dict[str, Any]: