feat: readiness sentinel for Kubernetes

entrypoint.sh creates /home/agent/vol/.openclaw-initializing at startup
and removes it just before launching the gateway. Pod is not marked
ready until init (volume copy + config baking) is fully complete.

deployment.yaml adds readinessProbe: exec test ! -f sentinel,
with initialDelaySeconds=5, periodSeconds=5, failureThreshold=60
(5 minute window for slow storage on first deploy).

deployment.yaml

@@ -64,6 +64,13 @@ spec:
             - name: vol
               mountPath: /home/agent/vol
 
+          readinessProbe:
+            exec:
+              command: ["test", "!", "-f", "/home/agent/vol/.openclaw-initializing"]
+            initialDelaySeconds: 5
+            periodSeconds: 5
+            failureThreshold: 60
+
           env:
 
             # ── Required ────────────────────────────────────────────