feat: brain-engine start/stop/status — lifecycle visible pour les forks

- start.sh: background par défaut, PID tracké, --foreground pour debug
- stop.sh: arrêt propre avec grace period 5s + force kill
- status.sh: running/stopped, vérification port, exit code scriptable
- getting-started: docs mis à jour (plus de nohup/kill manuels)
- .gitignore: .brain-engine.pid

brain-engine/status.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+# brain-engine/status.sh — Statut rapide
+# Usage : bash brain-engine/status.sh
+# Exit 0 si running, 1 si stopped — utilisable dans des scripts/briefings
+
+BRAIN_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+PIDFILE="$BRAIN_ROOT/.brain-engine.pid"
+PORT="${BRAIN_PORT:-7700}"
+
+if [ ! -f "$PIDFILE" ]; then
+    echo "brain-engine: stopped"
+    exit 1
+fi
+
+PID=$(cat "$PIDFILE")
+
+if kill -0 "$PID" 2>/dev/null; then
+    # Vérifier que le port répond
+    if curl -s --max-time 2 "http://localhost:$PORT/health" > /dev/null 2>&1; then
+        echo "brain-engine: running (PID $PID, port $PORT)"
+    else
+        echo "brain-engine: starting (PID $PID, port $PORT pas encore prêt)"
+    fi
+    exit 0
+else
+    rm -f "$PIDFILE"
+    echo "brain-engine: stopped (PID $PID stale — nettoyé)"
+    exit 1
+fi