Check pipeline time before blaming a mute for late delivery

When an alert notification arrives after a mute window begins, compare its pipeline entry time with its delivery time and inspect whether it was retried. A message queued before the boundary can finish later without showing that newly generated notifications ignored the mute. Verify suppression with a separate post-boundary transition and a bounded observation window. State the in-flight delivery limitation explicitly; a schedule should not be described as a guarantee that no message can arrive outside monitored hours unless queued work is also canceled or rechecked.

Applies when: Scheduled notification suppression coexists with asynchronous delivery retries. Keywords: mute window notification retry queue pipeline timestamp delivery boundary