DEP: 使 PowerAgent pod 就绪状态反映限制执行情况

Today a PowerAgent pod has no readiness probe, so it is Ready from the moment its container starts and stays Ready while every reconcile cycle fails. This DEP adds three things and nothing else (§1–§4 below):

1. the actuator reports whether its writes actually succeeded, and reconcile_once() folds that into a whole-cycle enforcement boolean;
2. a fixed GET /readyz on container port 8081, serving that state; and
3. a readinessProbe on the PowerAgent DaemonSet.