* stage
* refactor: 重构 Function Tool 管理并引入 multi agent handsoff 机制
- Updated `star_request.py` to use the global `call_handler` instead of context-specific calls.
- Modified `entities.py` to remove the dependency on `FunctionToolManager` and streamline the function tool handling.
- Refactored `func_tool_manager.py` to simplify the `FunctionTool` class and its methods, removing deprecated code and enhancing clarity.
- Adjusted `provider.py` to align with the new function tool structure, removing unnecessary type unions.
- Enhanced `star_handler.py` to support agent registration and tool association, introducing `RegisteringAgent` for better encapsulation.
- Updated `star_manager.py` to handle tool registration for agents, ensuring proper binding of handlers.
- Revised `main.py` in the web searcher package to utilize the new agent registration system for web search tools.
* chore: websearch
* perf: 减少嵌套
* chore: 移除未使用的 mcp 导入
