feat: enhance dynamic tool management with notifications and enable/disable

Summary

Enhance the Python SDK's dynamic tool management capabilities to match the TypeScript SDK by adding:

1. Automatic tools/list_changed notifications when tools are added/removed
2. Tool enable/disable functionality (temporary hiding without removal)

Background

The Python SDK currently supports adding and removing tools dynamically (see #1322), but lacks two key features present in the TypeScript SDK:

1. List Changed Notifications

The TypeScript SDK automatically sends notifications/tools/list_changed when tools are modified. This allows clients to know when they should refresh their tool list.

Python SDK gap: Currently, when calling add_tool() or remove_tool(), clients are not notified of the change and may show stale tool lists.

2. Enable/Disable Tools

The TypeScript SDK provides enable() and disable() methods on tools:

const tool = server.tool("myTool", ..., async () => { ... });
tool.disable()  // Hides from list_tools, blocks calls
tool.enable()   // Re-enables the tool
tool.remove()   // Permanently removes

Benefits:

• Temporarily hide tools without losing registration
• Re-enable tools without re-registering
• Useful for permission-based or state-based tool visibility

Python SDK gap: Only permanent removal via remove_tool() is supported. No way to temporarily disable/re-enable tools.

References

• Related PR: #1322 (adds remove_tool method)
• TypeScript SDK Dynamic Servers: https://github.com/modelcontextprotocol/typescript-sdk#dynamic-servers
• MCP spec supports notifications/tools/list_changed

先從 Python SDK 中 add_tool()、remove_tool()、list_tools() 和工具呼叫的入口開始，然後將其行為與所參照的 TypeScript SDK dynamic-server 實作進行比較。完成的標準是：新增和移除工具會觸發 tools/list_changed 通知，而停用的工具會被隱藏並阻擋，可以重新啟用，且仍然可以移除。