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>

gardener/gardener-poll.sh

@@ -4,7 +4,6 @@
 #
 # Cron: daily (or 2x/day). Handles lock management, escalation reply
 # injection, and delegates backlog grooming to gardener-agent.sh.
-# Then processes dev-agent CI escalations via the recipe engine.
 #
 # Grooming (delegated to gardener-agent.sh):
 #   - Duplicate titles / overlapping scope
@@ -12,13 +11,6 @@
 #   - Stale issues (no activity > 14 days)
 #   - Blockers starving the factory
 #   - Tech-debt promotion / dust bundling
-#
-# CI escalation (recipe-driven, handled here):
-#   - ShellCheck per-file sub-issues
-#   - Generic CI failure issues
-#   - Chicken-egg CI handling
-#   - Cascade rebase + retry merge
-#   - Flaky test quarantine
 # =============================================================================
 set -euo pipefail
 

gardener/gardener-run.sh

@@ -51,7 +51,7 @@ model: opus
 ---
 
 Periodic gardener housekeeping run. The action-agent reads \`formulas/run-gardener.toml\`
-and executes the steps: preflight, grooming, blocked-review, CI escalation recipes,
+and executes the steps: preflight, grooming, blocked-review,
 AGENTS.md update, and commit-and-pr.
 
 Filed automatically by \`gardener-run.sh\`."