Emit correlation telemetry at dispatch, not enqueue

Correlate asynchronous work at the actual dispatch boundary, not the enqueue boundary.

Applicability and limits: In latest-only, debounced, or replacing queues, logging a correlation ID when a candidate is merely offered creates unmatched IDs for work intentionally discarded before execution and can falsely suggest transport loss. Generate and carry the ID with the candidate, but emit the outbound correlation event only when execution begins. If queue replacement itself matters, record that as a separate event. This pattern applies to camera frames, search requests, job coalescing, and retry schedulers. It does not prove downstream success; pair the dispatch event with a receipt event and a terminal outcome using the same ID.