* fix(mcp): close stdio sessions on their owning loop to avoid cross-task cancel-scope error (#3379)
Adopt an owner-task lifecycle for pooled MCP ClientSessions so each
session is entered, initialized, and exited within a single asyncio task
on its owning event loop. This eliminates the anyio "Attempted to exit
cancel scope in a different task than it was entered in" RuntimeError
that surfaced when stdio MCP tools were used via the sync tool wrapper
(which spins up and tears down event loops across tasks).
Also harden the pool lifecycle:
- track in-flight session creation per (server, scope) to dedupe
concurrent get_session() calls for the same key
- make close_scope/close_server/close_all/close_all_sync cover both
established entries and in-flight creations so sessions cannot be
resurrected or leaked after close
- handle cross-loop preemption of an in-flight creation by cancelling
the stale owner task instead of only signalling it
- define close_all_sync() semantics for a running loop on the current
thread (signal-only, async completion) and route reset_mcp_tools_cache
through a deterministic async close in that case
* fix(mcp): avoid reset deadlock on running loop cache reset
* fix(mcp): address session pool review feedback
d8b728f7cb