reliability: add warm-pool outbox only for a proven recovery gap

[Brad-Edwards]

Follow-up to #2076. Move warm-pool lifecycle transitions to the shared transactional outbox only if the existing reconciler and durable state cannot recover a demonstrated lost or duplicated operation.

Acceptance

• Reproduce the failure with the current CLAIMED and RETIRING recovery path.
• Record the state change and retryable intent atomically without adding a second lifecycle authority.
• Prove restart, duplicate dispatch, and partial failure converge without orphaned warm ranges.