Resume Autopilot

Reset the caller's Autonomous streak in this chat and re-arm the reply.

Setting autopilot_resumed_at is what makes one click reset BOTH bounds: eligibility ignores every message at or before that instant, so the turn count restarts at zero and the time budget restarts from the next reply.

Clearing the guard is not enough on its own. Nothing else would fire until a brand-new inbound message arrived, so the user would click "keep going" and watch the conversation stay exactly as stopped as it was - the same dead end, one click later. The resume therefore re-enqueues the auto-reply for the conversation's current tail.