feat(auto-review) short-circuit (#18890)

## Summary
Short circuit the convo if auto-review hits too many denials

## Testing
- [x] Added unit tests

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/app-server-protocol/schema/json/ServerNotification.json

@@ -1704,6 +1704,23 @@
       ],
       "type": "string"
     },
+    "GuardianWarningNotification": {
+      "properties": {
+        "message": {
+          "description": "Concise guardian warning message for the user.",
+          "type": "string"
+        },
+        "threadId": {
+          "description": "Thread target for the guardian warning.",
+          "type": "string"
+        }
+      },
+      "required": [
+        "message",
+        "threadId"
+      ],
+      "type": "object"
+    },
     "HookCompletedNotification": {
       "properties": {
         "run": {
@@ -5342,6 +5359,26 @@
       "title": "WarningNotification",
       "type": "object"
     },
+    {
+      "properties": {
+        "method": {
+          "enum": [
+            "guardianWarning"
+          ],
+          "title": "GuardianWarningNotificationMethod",
+          "type": "string"
+        },
+        "params": {
+          "$ref": "#/definitions/GuardianWarningNotification"
+        }
+      },
+      "required": [
+        "method",
+        "params"
+      ],
+      "title": "GuardianWarningNotification",
+      "type": "object"
+    },
     {
       "properties": {
         "method": {