fix: wait for gateway ready before post-install model validation

Root cause: gateway restart is async (systemd), but validateNoReplyModelAvailable()
ran immediately after, hitting a race condition where the new gateway process
hadn't finished initializing yet. This caused 'model not listed' validation
failures, triggering config rollback even though the config was correct.

Changes:
- Add waitForGatewayReady() that polls 'openclaw gateway status' for RPC probe
- Add retry loop (5 attempts, 2s interval) to validateNoReplyModelAvailable()
- Fix CONFIG.example.json: contextWindow 4096->200000, maxTokens 64->8192
  (OpenClaw requires minimum 16000 contextWindow)

no-reply-api/package-lock.json

@@ -0,0 +1,12 @@
+{
+  "name": "whispergate-no-reply-api",
+  "version": "0.1.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "whispergate-no-reply-api",
+      "version": "0.1.0"
+    }
+  }
+}