slo-mo - request-timeout probe

GET /wait?d=<dur>            hold the response for d, then answer with JSON
                             d: Go duration (5m, 330s, 1h) or bare seconds (360); 0 answers at once
GET /wait?d=<dur>&tick=<dur> same, but stream one "." every tick so the response is a trickle, not silence
GET /healthz  /readyz        liveness / readiness, 200 "ok"
GET /.well-known/live  /.well-known/ready   ODJ default probe paths, same as above