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/ext/extension-api/src/registry.rs

@@ -2,8 +2,6 @@ use std::sync::Arc;
 
 use codex_protocol::protocol::ReviewDecision;
 
-use crate::ApprovalPolicyContributor;
-use crate::ApprovalRequirement;
 use crate::ApprovalReviewContributor;
 use crate::ConfigContributor;
 use crate::ContextContributor;
@@ -35,7 +33,6 @@ impl<C: Sync> Default for ExtensionRegistryBuilder<C> {
                 config_contributors: Vec::new(),
                 token_usage_contributors: Vec::new(),
                 skill_invocation_contributors: Vec::new(),
-                approval_policy_contributors: Vec::new(),
                 approval_review_contributors: Vec::new(),
                 context_contributors: Vec::new(),
                 mcp_server_contributors: Vec::new(),
@@ -66,11 +63,6 @@ impl<C: Sync> ExtensionRegistryBuilder<C> {
         Arc::clone(&self.registry.event_sink)
     }
 
-    /// Registers one thread-scoped approval-policy contributor.
-    pub fn approval_policy_contributor(&mut self, contributor: Arc<dyn ApprovalPolicyContributor>) {
-        self.registry.approval_policy_contributors.push(contributor);
-    }
-
     /// Registers one approval-review contributor.
     pub fn approval_review_contributor(&mut self, contributor: Arc<dyn ApprovalReviewContributor>) {
         self.registry.approval_review_contributors.push(contributor);
@@ -161,7 +153,6 @@ pub struct ExtensionRegistry<C: Sync> {
     tool_contributors: Vec<Arc<dyn ToolContributor>>,
     tool_lifecycle_contributors: Vec<Arc<dyn ToolLifecycleContributor>>,
     turn_item_contributors: Vec<Arc<dyn TurnItemContributor>>,
-    approval_policy_contributors: Vec<Arc<dyn ApprovalPolicyContributor>>,
     approval_review_contributors: Vec<Arc<dyn ApprovalReviewContributor>>,
 }
 
@@ -196,18 +187,6 @@ impl<C: Sync> ExtensionRegistry<C> {
         &self.skill_invocation_contributors
     }
 
-    /// Resolves the strongest approval requirement for the current thread.
-    pub fn approval_requirement(&self, thread_store: &ExtensionData) -> ApprovalRequirement {
-        if self.approval_policy_contributors.iter().any(|contributor| {
-            contributor.approval_requirement(thread_store)
-                == ApprovalRequirement::RequireAutomaticReview
-        }) {
-            ApprovalRequirement::RequireAutomaticReview
-        } else {
-            ApprovalRequirement::Default
-        }
-    }
-
     /// Claims the first rendered approval-review prompt accepted by an
     /// installed contributor.
     pub async fn approval_review(