Let extensions resolve approval reviews before Guardian (#38592)

## What changed

- Give approval review contributors the first opportunity to resolve an action when automatic review is not required for the model.
- Return an extension's decision directly and fall back to Guardian when no extension claims the review.
- Update Guardian V2 to approve actions below its risk threshold through the review contributor API, and remove the extension approval-policy API.

## Testing

- Verify that an extension approval bypasses both the Guardian model call and the user approval prompt.
- Cover Guardian V2 review decisions for low-risk, high-risk, and disabled threads.

GitOrigin-RevId: 5be56941143aff6f358b75b5f8101b7c047147ae

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

@@ -2512,9 +2512,7 @@ impl Session {
             });
         };
 
-        if crate::guardian::routes_approval_to_guardian(turn_context.as_ref())
-            || self.extension_strict_auto_review_enabled().await
-        {
+        if crate::guardian::routes_approval_to_guardian(turn_context.as_ref()) {
             let originating_turn_state = {
                 let active = self.active_turn.lock().await;
                 active.as_ref().map(|active| Arc::clone(&active.turn_state))
@@ -2853,41 +2851,11 @@ impl Session {
     pub(crate) async fn active_turn_context_and_strict_auto_review(
         &self,
     ) -> Option<(Arc<TurnContext>, bool)> {
-        let extension_strict_auto_review = self.extension_strict_auto_review_enabled().await;
         let active = self.active_turn.lock().await;
         let active = active.as_ref()?;
         let turn_context = Arc::clone(&active.task.as_ref()?.turn_context);
         let ts = active.turn_state.lock().await;
-        Some((
-            turn_context,
-            ts.strict_auto_review_enabled() || extension_strict_auto_review,
-        ))
-    }
-
-    pub(crate) async fn extension_strict_auto_review_enabled(&self) -> bool {
-        if self
-            .services
-            .extensions
-            .approval_requirement(&self.services.thread_extension_data)
-            != codex_extension_api::ApprovalRequirement::RequireAutomaticReview
-        {
-            return false;
-        }
-
-        let state = self.state.lock().await;
-        let configuration = &state.session_configuration;
-        !configuration.trusted_guardian_reviewer
-            && configuration
-                .original_config_do_not_use
-                .features
-                .enabled(Feature::GuardianApproval)
-            && configuration
-                .original_config_do_not_use
-                .config_layer_stack
-                .requirements()
-                .approvals_reviewer
-                .can_set(&ApprovalsReviewer::AutoReview)
-                .is_ok()
+        Some((turn_context, ts.strict_auto_review_enabled()))
     }
 
     pub(crate) async fn granted_session_permissions(