#5463 "Acknowledgements on record: an event and who did it", step 1 of
milestone 499 "Alerts you can trust". The live walk in #5461 found that
acknowledging changed only the alert's current state: once it resolved,
nothing said who had acknowledged it or when.
- alert_events.actor_id (migration 0040): the person behind a transition.
- Acknowledging writes a firing → acknowledged event by the acknowledger.
- A rule edit, disable or enable that resets an alert carries its actor
(web and MCP alike).
- The history page notes "acknowledged by X" and "rule disabled by X"; MCP
get_alert_history returns `by`.
- One usernames() helper in alerts.service, used by the active list, the
history page and the MCP tools.
- docs/core/alerting.md: the state diagram no longer shows an acknowledged
alert re-firing, and says what an event records.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
