AGENTS.md autonomous-PR-maintenance proposal wait-watchdog: verify Carson decision within 72h of surfacing

Follow-up from 2026-07-08 09:57Z AGENTS.md proposal DM (slack_ts 1783504626.091579). At lease: (1) read last 25 Carson DMs since 2026-07-08T09:57Z for approve/modify/forbid response; (2) if approved, apply the AGENTS.md edit in a fresh PR on kai/agents-md-autonomous-pr-maintenance branch and link the PR to Carson; (3) if modified, apply requested modifications, PATCH the proposal file, and re-surface; (4) if forbidden, delete or annotate the proposal file with the forbid decision and record the rule as retracted; (5) if no response, do NOT re-DM (ping-once-back-off) — post a task event NO_RESPONSE_HOLD and re-arm +72h, up to 2 more re-arms (N=3 max); on 3rd no-response, roll into next standup as a status line, do not proactively DM. Note: PR #12919 merged 2026-07-07 22:32Z (Carson-merged), so this rule is retrospective-not-blocking; there is no urgency, discretion favors patience.