A queued custom-resource (Custom::*) Lambda invocation. Built by
create_custom_resource / delete_custom_resource when
defer_custom_invokes is set, drained and tokio::spawned off the request
path so a cold image pull never blocks the client or the CFN state lock.
A container-backed resource the synchronous provisioning pass inserted as a
“creating” record that now needs a real backing container. Drained by
CreateStack after provisioning and backgrounded so the stack create call
never blocks on a container boot/pull.
A container-backed resource the synchronous delete pass removed from memory
that still has a REAL backing container to reap. Drained by the
CloudFormation delete path (stack delete / update-removed) and backgrounded
so the stack op never blocks on a container stop. Mirrors
ContainerSpawnIntent for teardown.