reap_terminal was one unbatched DELETE with no updated_at index — a full scan and
long-held lock over a large backlog (audit M5). Migration 0040 adds a partial
index on (updated_at) WHERE state IN ('done','dead'); reap_terminal now deletes in
bounded 5k batches. Existing tests green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
