Route opted-in MCP elicitations through Guardian (#19431)

# Motivation

Browser Use origin-access prompts are MCP elicitations, not direct
tool-call approval prompts, so they were bypassing the Guardian approval
path. We need a generic opt-in that lets eligible MCP elicitations use
Guardian when the current turn already routes approvals there.

# Description

Add a generic elicitation reviewer hook in codex-mcp and wire codex-core
to pass a Guardian reviewer callback when creating the MCP connection
manager. The reviewer validates explicit mcp_tool_call opt-in metadata,
builds a Guardian MCP tool-call review request from
server/tool/connector metadata and tool params, and maps Guardian
approval, denial, timeout, and cancellation decisions back to MCP
elicitation responses.

The new option to trigger this in the `_meta` object is:
```
"codex_request_type": "approval_request",
```

# Testing

- RUST_MIN_STACK=8388608 NEXTEST_STATUS_LEVEL=leak cargo nextest run
--no-fail-fast --cargo-profile ci-test --test-threads 2
- cargo clippy --tests -- -D warnings
- cargo fmt -- --config imports_granularity=Item --check
- cargo shear
- pnpm run format
- python3 .github/scripts/verify_cargo_workspace_manifests.py
- python3 .github/scripts/verify_tui_core_boundary.py
- python3 .github/scripts/verify_bazel_clippy_lints.py
- git diff --check

codex-rs/codex-mcp/src/elicitation.rs

@@ -24,6 +24,7 @@ use codex_protocol::protocol::Event;
 use codex_protocol::protocol::EventMsg;
 use codex_rmcp_client::ElicitationResponse;
 use codex_rmcp_client::SendElicitation;
+use futures::future::BoxFuture;
 use futures::future::FutureExt;
 use rmcp::model::CreateElicitationRequestParams;
 use rmcp::model::ElicitationAction;
@@ -31,24 +32,43 @@ use rmcp::model::RequestId;
 use tokio::sync::Mutex;
 use tokio::sync::oneshot;
 
+#[derive(Debug, Clone)]
+pub struct ElicitationReviewRequest {
+    pub server_name: String,
+    pub request_id: RequestId,
+    pub elicitation: CreateElicitationRequestParams,
+}
+
+pub trait ElicitationReviewer: Send + Sync {
+    fn review(
+        &self,
+        request: ElicitationReviewRequest,
+    ) -> BoxFuture<'static, Result<Option<ElicitationResponse>>>;
+}
+
+pub type ElicitationReviewerHandle = Arc<dyn ElicitationReviewer>;
+
 #[derive(Clone)]
 pub(crate) struct ElicitationRequestManager {
     requests: Arc<Mutex<ResponderMap>>,
     pub(crate) approval_policy: Arc<StdMutex<AskForApproval>>,
     pub(crate) permission_profile: Arc<StdMutex<PermissionProfile>>,
     auto_deny: Arc<StdMutex<bool>>,
+    reviewer: Option<ElicitationReviewerHandle>,
 }
 
 impl ElicitationRequestManager {
     pub(crate) fn new(
         approval_policy: AskForApproval,
         permission_profile: PermissionProfile,
+        reviewer: Option<ElicitationReviewerHandle>,
     ) -> Self {
         Self {
             requests: Arc::new(Mutex::new(HashMap::new())),
             approval_policy: Arc::new(StdMutex::new(approval_policy)),
             permission_profile: Arc::new(StdMutex::new(permission_profile)),
             auto_deny: Arc::new(StdMutex::new(false)),
+            reviewer,
         }
     }
 
@@ -89,6 +109,7 @@ impl ElicitationRequestManager {
         let approval_policy = self.approval_policy.clone();
         let permission_profile = self.permission_profile.clone();
         let auto_deny = self.auto_deny.clone();
+        let reviewer = self.reviewer.clone();
         Box::new(move |id, elicitation| {
             let elicitation_requests = elicitation_requests.clone();
             let tx_event = tx_event.clone();
@@ -96,6 +117,7 @@ impl ElicitationRequestManager {
             let approval_policy = approval_policy.clone();
             let permission_profile = permission_profile.clone();
             let auto_deny = auto_deny.clone();
+            let reviewer = reviewer.clone();
             async move {
                 let auto_deny = auto_deny
                     .lock()
@@ -138,6 +160,17 @@ impl ElicitationRequestManager {
                     });
                 }
 
+                if let Some(reviewer) = reviewer.as_ref() {
+                    let request = ElicitationReviewRequest {
+                        server_name: server_name.clone(),
+                        request_id: id.clone(),
+                        elicitation: elicitation.clone(),
+                    };
+                    if let Some(response) = reviewer.review(request).await? {
+                        return Ok(response);
+                    }
+                }
+
                 let request = match elicitation {
                     CreateElicitationRequestParams::FormElicitationParams {
                         meta,