* fix: exit MCP anyio contexts in the lifecycle task on disable
#9070 moved MCP shutdown cleanup into the per-server lifecycle task so
that the anyio cancel scopes entered in connect_to_server() are exited
from the task that entered them. Running the cleanup through
asyncio.shield() defeats that: shield wraps the coroutine in a new
task, so disabling a server still fails with "Attempted to exit cancel
scope in a different task than it was entered in" and leaves the scope
state corrupted -- the failure mode behind the CPU spin reported in
#9068.
Await _terminate_mcp_client() directly instead. The graceful disable
path has no cancellation in flight, and on forced shutdown the
lifecycle task still runs its finally block in-task, so the shield only
served to break task affinity.
Closes#9068
* fix: absorb late cancellations during MCP shutdown cleanup
A cancellation delivered while the lifecycle task is already running its
finally-block cleanup would abort _terminate_mcp_client() halfway,
stranding the runtime entry and the MCP transport. Retry the cleanup in
the same task and uncancel() the absorbed request instead, so a forced
shutdown can no longer skip it.
* fix: guard Task.uncancel() for Python 3.10 runtimes
Task.uncancel() only exists on Python 3.11+. On 3.10 absorbing the
CancelledError is sufficient, so skip the call when unavailable.
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