chore(dev): run the mock-metrics emitter under supervisor (single, persistent)

Manage clusev:mock-metrics as a supervisor program in the dev image so exactly
one emitter runs and survives container recreates (no stray exec -d processes).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docker/supervisor/supervisord.dev.conf

@@ -35,6 +35,20 @@ environment=HOME="/home/app",USER="app",NPM_CONFIG_CACHE="/home/app/.npm"
 autorestart=true
 startretries=3
 startsecs=10
+
+; Dev metrics emitter (mock CPU+MEM over Reverb) — replaced by the real MetricsPoller (SSH) later.
+[program:metrics]
+command=php artisan clusev:mock-metrics --interval=2
+directory=/var/www/html
+user=app
+environment=HOME="/home/app",USER="app"
+autostart=true
+autorestart=true
+startsecs=5
+stdout_logfile=/dev/stdout
+stdout_logfile_maxbytes=0
+stderr_logfile=/dev/stderr
+stderr_logfile_maxbytes=0
 stdout_logfile=/dev/stdout
 stdout_logfile_maxbytes=0
 stderr_logfile=/dev/stderr