Three fixes for concurrent MCP server spawn races in register_mcp_servers()
and discover_mcp_tools():
1. register_mcp_servers: add k not in _server_connecting guard to the
new_servers filter. Without this, a concurrent second call sees the
same servers as 'new' and spawns duplicate stdio subprocesses.
2. discover_mcp_tools: same _server_connecting guard in the
new_server_names filter. This entry point is called from CLI, TUI,
gateway, and cron — any two racing would double-spawn.
3. Stale _server_connecting cleanup on TimeoutError/InterruptedError.
When _run_on_mcp_loop times out or is interrupted, _discover_all's
gather may not have finished, leaving entries stranded in
_server_connecting that block future reconnection attempts. The
cleanup clears only entries added by this call (not external ones),
logs a warning, and records connect errors.
Salvage of #58879 by @nanami7777777 (superset of #58867 by @liuhao1024).
Adapted to current main which has evolved significantly since July 5.
Closes#58862Closes#58867Closes#58879
b5ca19118e