- executeOnSession's runQueued callback now re-checks sessions.get(sessionId) === session at slot entry and before the dead-kernel replace retry; if the session was removed by disposeAllKernelSessions / disposeKernelSessionsByOwner / resetSession during the queue wait, the queued caller now rejects with PythonExecutionCancelledError instead of spawning an untracked replacement kernel on a stale session object.
- Both dispose paths now inspect KernelShutdownResult.confirmed and retain (or re-insert) sessions whose shutdown was unconfirmed or rejected, logging a warn so a later dispose can retry the kernel instead of orphaning the subprocess.