Fixes#9930
When an agent session is interrupted (Ctrl+C or gateway timeout), the
current thread's interrupt flag is set in _interrupted_threads. asyncio
executor threads are pooled and reused across sessions, so a thread that
carried an interrupt flag from a prior session will immediately cancel
any new asyncio work dispatched to it — including MCP server discovery.
Fix: in register_mcp_servers(), temporarily clear the interrupt flag on
the current thread before running _discover_all(), then restore it
afterward in a finally block so the original interrupt state is not lost.
9575bce6ca