Receive a terminal operation or output event

Revero delivers terminal events at least once and without ordering guarantees. Verify Flyt-Signature against the exact request bytes before decoding this envelope, deduplicate on the event ID, return a 2xx response quickly, and reconcile through the authenticated links. Revero retries timeouts, 429 and 5xx responses; it stops on other 4xx responses and does not follow redirects.