feat(phase4): add gateway:startup hook for auto-starting watcher daemon

- hooks/status-watcher-hook/HOOK.md — events: ["gateway:startup"], required env vars
- hooks/status-watcher-hook/handler.js — checks PID file, spawns watcher-manager.js detached
- Deployed hook to /home/node/.openclaw/workspace/hooks/status-watcher-hook/
- make check passes

hooks/status-watcher-hook/HOOK.md

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+# status-watcher-hook
+
+Auto-starts the Live Status v4 daemon when the OpenClaw gateway starts.
+
+## Events
+
+```json
+["gateway:startup"]
+```
+
+## Description
+
+On gateway startup, this hook checks whether the status-watcher daemon is already
+running (via PID file). If not, it spawns `watcher-manager.js start` as a detached
+background process, then exits immediately. The daemon continues running independently
+of this hook handler.
+
+## Required Environment Variables
+
+The following environment variables must be set for the watcher to function:
+
+```
+MM_TOKEN         Mattermost bot token
+MM_URL           Mattermost base URL (e.g. https://slack.solio.tech)
+TRANSCRIPT_DIR   Path to agent sessions directory
+SESSIONS_JSON    Path to sessions.json
+```
+
+Optional (defaults shown):
+
+```
+THROTTLE_MS               500
+IDLE_TIMEOUT_S            60
+MAX_STATUS_LINES          15
+MAX_ACTIVE_SESSIONS       20
+MAX_MESSAGE_CHARS         15000
+HEALTH_PORT               9090
+LOG_LEVEL                 info
+PID_FILE                  /tmp/status-watcher.pid
+CIRCUIT_BREAKER_THRESHOLD 5
+CIRCUIT_BREAKER_COOLDOWN_S 30
+```
+
+## Installation
+
+This hook is deployed automatically by `install.sh` or `deploy-to-agents.sh`.
+To deploy manually:
+
+```sh
+cp -r hooks/status-watcher-hook /home/node/.openclaw/workspace/hooks/
+```
+
+The hook activates on the next gateway startup.

hooks/status-watcher-hook/handler.js

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+'use strict';
+
+/**
+ * status-watcher-hook/handler.js
+ *
+ * Spawns the Live Status v4 watcher-manager daemon on gateway startup.
+ *
+ * Events: ["gateway:startup"]
+ *
+ * Behavior:
+ *   1. Check PID file — if watcher is already running, do nothing.
+ *   2. If not running, spawn watcher-manager.js as a detached background process.
+ *   3. The hook handler returns immediately; the daemon runs independently.
+ */
+
+/* eslint-disable no-console */
+
+const fs = require('fs');
+const path = require('path');
+const { spawn } = require('child_process');
+
+// PID file location (must match watcher-manager.js default)
+const PID_FILE = process.env.PID_FILE || '/tmp/status-watcher.pid';
+
+// Path to watcher-manager.js (relative to this hook file's location)
+// Hook is in: workspace/hooks/status-watcher-hook/handler.js
+// Watcher is in: workspace/projects/openclaw-live-status/src/watcher-manager.js
+const WATCHER_PATH = path.resolve(
+  __dirname,
+  '../../projects/openclaw-live-status/src/watcher-manager.js',
+);
+
+/**
+ * Check if a process is alive given its PID.
+ * Returns true if process exists and is running.
+ */
+function isProcessRunning(pid) {
+  try {
+    process.kill(pid, 0);
+    return true;
+  } catch (_err) {
+    return false;
+  }
+}
+
+/**
+ * Check if the watcher daemon is already running via PID file.
+ * Returns true if running, false if not (or PID file stale/missing).
+ */
+function isWatcherRunning() {
+  try {
+    // eslint-disable-next-line security/detect-non-literal-fs-filename
+    const pidStr = fs.readFileSync(PID_FILE, 'utf8').trim();
+    const pid = parseInt(pidStr, 10);
+    if (isNaN(pid) || pid <= 0) return false;
+    return isProcessRunning(pid);
+  } catch (_err) {
+    // PID file missing or unreadable — watcher is not running
+    return false;
+  }
+}
+
+/**
+ * Spawn the watcher daemon as a detached background process.
+ * The parent (this hook handler) does not wait for it.
+ */
+function spawnWatcher() {
+  if (!fs.existsSync(WATCHER_PATH)) {
+    console.error('[status-watcher-hook] watcher-manager.js not found at:', WATCHER_PATH);
+    console.error('[status-watcher-hook] Deploy the live-status project first: see install.sh');
+    return;
+  }
+
+  console.log('[status-watcher-hook] Starting Live Status v4 watcher daemon...');
+
+  const child = spawn(process.execPath, [WATCHER_PATH, 'start'], {
+    detached: true,
+    stdio: 'ignore',
+    env: process.env,
+  });
+
+  child.unref();
+
+  console.log(
+    '[status-watcher-hook] Watcher daemon spawned (PID will be written to',
+    PID_FILE + ')',
+  );
+}
+
+/**
+ * Hook entry point — called by OpenClaw on gateway:startup event.
+ */
+async function handle(_event) {
+  if (isWatcherRunning()) {
+    console.log('[status-watcher-hook] Watcher already running, skipping spawn.');
+    return;
+  }
+
+  spawnWatcher();
+}
+
+module.exports = { handle };