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

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

## Testing
- [x] Added unit tests

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

codex-rs/core/src/session/session.rs

@@ -695,6 +695,8 @@ impl Session {
             models_manager: Arc::clone(&models_manager),
             tool_approvals: Mutex::new(ApprovalStore::default()),
             guardian_rejections: Mutex::new(HashMap::new()),
+            guardian_rejection_circuit_breaker: Mutex::new(Default::default()),
+            runtime_handle: tokio::runtime::Handle::current(),
             skills_manager,
             plugins_manager: Arc::clone(&plugins_manager),
             mcp_manager: Arc::clone(&mcp_manager),