Snooze Catalog Entry

Snooze the outstanding update notification for a catalog entry (C1, #925).

Operator action (events:write): quiet the "update available" badge for a known-and-accepted upstream change without adopting it. Body is optional — omit or send {"snoozed_until": null} to mute until a newer upstream digest lands (the primary per-API affordance); send an ISO-8601 snoozed_until for a time-boxed snooze. A genuinely newer upstream change re-lights the badge automatically.