- disposeAllKernelSessions removes sessions from the registry before awaiting shutdown, preventing queued work from seeing a registered-but-disposing session and spawning a replacement kernel.
- replaceSessionKernel re-checks registry membership after old-kernel shutdown and after starting a replacement, shutting the replacement down if the session was disposed mid-replace.
- owner-scoped disposal now preserves ownerIds when shutdown is unconfirmed so a later disposeKernelSessionsByOwner(ownerId) can retry.