Independent readiness snapshot returned by Worker.pullRegistrationState.
Readonly
Latches after a STEP_AND_RPC stream and, when reserved, an RPC_ONLY stream register; false on a permanent error without a registered stream of that kind.
Slot-kind snapshots in registration order: STEP_AND_RPC, then RPC_ONLY when configured.
Independent readiness snapshot returned by Worker.pullRegistrationState.