Emit(ctx, Event) is the single decision point for who is told what: it
reads the event type's notification_prefs row and stores one pending
notification_outbox row per enabled channel, keyed by (event_key, channel)
with ON CONFLICT DO NOTHING, so a duplicate key never adds or resets a row.
The worker, started and stopped by cmd/server with the job runner, leases
due rows with a conditional update, delivers them through the Sender
registered for their channel, and marks them sent, or retries with a
backoff of 1 minute doubling to 1 hour until 24 hours after creation,
then marks them failed with last_error. A channel with no registered
sender fails its rows with an explicit error.
Maestro task addeb256-a4d4-4acf-8acd-6b6778d967ee.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
