chore: gardener housekeeping 2026-03-21

Progressive disclosure split of AGENTS.md (487→152 lines):
- Extracted per-directory AGENTS.md files for all 8 agents + lib/
- Root AGENTS.md now serves as a table of contents with summary table
- All watermarks updated to 16e430e

Grooming results:
- Promoted #469 (WATCH flow missing curl) and #436 (idle_pane_count bug) to backlog
- 12 dust items classified, no groups ripe for bundling yet
- No blocked issues, no AD violations

supervisor/AGENTS.md

@@ -0,0 +1,53 @@
+<!-- last-reviewed: 16e430ebce905cf722f91ae1f873faea1c64d890 -->
+# Supervisor Agent
+
+**Role**: Health monitoring and auto-remediation, executed as a formula-driven
+Claude agent. Collects system and project metrics via a bash pre-flight script,
+then runs an interactive Claude session (sonnet) that assesses health, auto-fixes
+issues, escalates via Matrix, and writes a daily journal.
+
+**Trigger**: `supervisor-run.sh` runs every 20 min via cron. It creates a tmux
+session with `claude --model sonnet`, injects `formulas/run-supervisor.toml`
+with pre-collected metrics as context, monitors the phase file, and cleans up
+on completion or timeout (20 min max session). No action issues — the supervisor
+runs directly from cron like the planner and predictor.
+
+**Key files**:
+- `supervisor/supervisor-run.sh` — Cron wrapper + orchestrator: lock, memory guard,
+  runs preflight.sh, sources disinto project config, creates tmux session, injects
+  formula prompt with metrics, monitors phase file, handles crash recovery via
+  `run_formula_and_monitor`
+- `supervisor/preflight.sh` — Data collection: system resources (RAM, disk, swap,
+  load), Docker status, active tmux sessions + phase files, lock files, agent log
+  tails, CI pipeline status, open PRs, issue counts, stale worktrees, blocked
+  issues, Matrix escalation replies
+- `formulas/run-supervisor.toml` — Execution spec: five steps (preflight review,
+  health-assessment, decide-actions, report, journal) with `needs` dependencies.
+  Claude evaluates all metrics and takes actions in a single interactive session
+- `supervisor/journal/*.md` — Daily health logs from each supervisor run (local,
+  committed periodically)
+- `supervisor/PROMPT.md` — Best-practices reference for remediation actions
+- `supervisor/best-practices/*.md` — Domain-specific remediation guides (memory,
+  disk, CI, git, dev-agent, review-agent, codeberg)
+- `supervisor/supervisor-poll.sh` — Legacy bash orchestrator (superseded by
+  supervisor-run.sh + formula)
+
+**Alert priorities**: P0 (memory crisis), P1 (disk), P2 (factory stopped/stalled),
+P3 (degraded PRs, circular deps, stale deps), P4 (housekeeping).
+
+**Matrix integration**: The supervisor has its own Matrix thread. Posts health
+summaries when there are changes, escalates P0-P2 issues, and processes replies
+from humans ("ignore disk warning", "kill that agent", "what's stuck?"). The
+Matrix listener routes thread replies to `/tmp/supervisor-escalation-reply`,
+which `supervisor-run.sh` consumes atomically on each run.
+
+**Environment variables consumed**:
+- `CODEBERG_TOKEN`, `CODEBERG_REPO`, `CODEBERG_API`, `PROJECT_NAME`, `PROJECT_REPO_ROOT`
+- `PRIMARY_BRANCH`, `CLAUDE_MODEL` (set to sonnet by supervisor-run.sh)
+- `WOODPECKER_TOKEN`, `WOODPECKER_SERVER`, `WOODPECKER_DB_PASSWORD`, `WOODPECKER_DB_USER`, `WOODPECKER_DB_HOST`, `WOODPECKER_DB_NAME` — CI database queries
+- `MATRIX_TOKEN`, `MATRIX_ROOM_ID`, `MATRIX_HOMESERVER` — Matrix notifications + human input
+
+**Lifecycle**: supervisor-run.sh (cron */20) → lock + memory guard → run
+preflight.sh (collect metrics) → consume escalation replies → load formula +
+context → create tmux session → Claude assesses health, auto-fixes, posts
+Matrix summary, writes journal → `PHASE:done`.