FastMCP.run(transport="stdio") produces noisy traceback on KeyboardInterrupt instead of clean exit

Initial Checks

• I confirm that I'm using the latest version of MCP Python SDK
• I confirm that I searched for my issue in https://github.com/modelcontextprotocol/python-sdk/issues before opening this issue

Description

Running a FastMCP stdio server from the terminal and interrupting with Ctrl-C produces a multi-frame traceback through anyio.run() → asyncio.runners → mcp.server.lowlevel.server.run → anyio.streams.memory.receive. The server is correctly waiting on stdin in an async loop; the trace surfaces because anyio/asyncio don't suppress the cancellation chain. Suggested fix: catch KeyboardInterrupt (or asyncio.CancelledError at the outer boundary) inside FastMCP.run and exit cleanly. Cosmetic but reduces user confusion when testing MCP servers from the terminal.

Example Code

Python & MCP Python SDK

Python 3.13.5
MCP Python SDK 1.27.1

Commencez par reproduire le comportement de Ctrl-C pour un serveur stdio FastMCP, puis suivez FastMCP.run à travers mcp.server.lowlevel.server.run et le chemin de réception en mémoire d'anyio. La correction est terminée lorsque l'interruption du serveur se termine proprement sans traceback, tandis que le comportement normal d'arrêt reste inchangé.