PR #12919 merge audit re-arm: check merge state; single 3-option DM only if >72h since notify-on-ready and material delta

Fired from 2026-07-03 04:10 UTC self-reflection cron. #12923 MERGED 2026-07-02T20:36:22Z (6h after prior audit fired at 14:10Z — captures the stale-audit lesson). #12919 remains OPEN + APPROVED + MERGEABLE, updated 2026-07-01T22:09Z. Notify-on-ready was 2026-07-01T01:55Z (~54h stale at cron-fire). At lease: query #12919 merge state. If merged: task event, close. If still open at lease AND >72h from notify-on-ready AND no Kai DM to Carson referencing #12919 in last 24h (Core Rule #11 read last 25 DMs), send ONE 3-option in-thread ping (merge / hand off / hold). If dedupe-blocked, NO_SEND_DEDUPE + capture reasoning. Whichever path, on non-terminal outcome POST a follow-up audit task with trigger +24h.