chore: gardener housekeeping 2026-03-22

- Update all AGENTS.md watermarks to current HEAD (251d160)
- dev/AGENTS.md: document dev-poll's early direct-merge scan (before lock
  check) — approved PRs now merge without waiting for active dev sessions;
  chore/gardener PRs merge without issue numbers in branch name
- planner/AGENTS.md: document dispatch-idle-formulas phase (step 4); note
  that planner reads both factory and project-specific formulas; clarify
  that all planner artifacts use $PROJECT_REPO_ROOT, not $FACTORY_ROOT

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

dev/AGENTS.md

@@ -1,12 +1,15 @@
-<!-- last-reviewed: ac51497489abc5412bc47f451facc30b0455cbd2 -->
+<!-- last-reviewed: 251d160e213b19a4fcc0cd8f8e3be9ea3283887f -->
 # Dev Agent
 
 **Role**: Implement issues autonomously — write code, push branches, address
 CI failures and review feedback.
 
-**Trigger**: `dev-poll.sh` runs every 10 min via cron. It scans for ready
-backlog issues (all deps closed) or orphaned in-progress issues and spawns
-`dev-agent.sh <issue-number>`.
+**Trigger**: `dev-poll.sh` runs every 10 min via cron. It performs a direct-merge
+scan first (approved + CI green PRs — including chore/gardener PRs without issue
+numbers), then checks the agent lock and scans for ready backlog issues (all deps
+closed) or orphaned in-progress issues to spawn `dev-agent.sh <issue-number>`.
+The direct-merge scan runs before the lock check so approved PRs get merged even
+while a dev-agent session is active on another issue.
 
 **Key files**:
 - `dev/dev-poll.sh` — Cron scheduler: finds next ready issue, handles merge/rebase of approved PRs, tracks CI fix attempts