fix: address review — restore +x, guard double comment, update stale docs (#352)

- Restore executable bit on gardener/gardener-poll.sh (cron invokes it directly)
- Add _BLOCKED_POSTED guard to prevent duplicate diagnostic comments when
  both _on_phase_change(PHASE:crashed) and the belt-and-suspenders exit
  handler both call post_blocked_diagnostic()
- Update stale documentation:
  - gardener-run.sh: remove "CI escalation recipes" from issue body
  - AGENTS.md: update directory layout comment for gardener-poll.sh
  - gardener-poll.sh: remove recipe engine description from header

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -17,7 +17,7 @@ disinto/
 ├── dev/           dev-poll.sh, dev-agent.sh, phase-handler.sh — issue implementation
 ├── review/        review-poll.sh, review-pr.sh — PR review
 ├── gardener/      gardener-run.sh — files action issue for run-gardener formula
-│                  gardener-poll.sh, gardener-agent.sh — recipe engine + grooming
+│                  gardener-poll.sh, gardener-agent.sh — grooming
 ├── predictor/     predictor-run.sh — daily cron executor for run-predictor formula
 ├── planner/       planner-run.sh — direct cron executor for run-planner formula
 │                  planner/journal/ — daily raw logs from each planner run