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/connection_manager.rs

@@ -17,6 +17,7 @@ use crate::codex_apps::CodexAppsToolsCacheContext;
 use crate::codex_apps::CodexAppsToolsCacheKey;
 use crate::codex_apps::write_cached_codex_apps_tools_if_needed;
 use crate::elicitation::ElicitationRequestManager;
+use crate::elicitation::ElicitationReviewerHandle;
 use crate::mcp::CODEX_APPS_MCP_SERVER_NAME;
 use crate::mcp::ToolPluginProvenance;
 use crate::rmcp_client::AsyncManagedClient;
@@ -87,6 +88,7 @@ impl McpConnectionManager {
             elicitation_requests: ElicitationRequestManager::new(
                 approval_policy.value(),
                 permission_profile.get().clone(),
+                /*reviewer*/ None,
             ),
             startup_cancellation_token: CancellationToken::new(),
         }
@@ -157,13 +159,17 @@ impl McpConnectionManager {
         host_owned_codex_apps_enabled: bool,
         tool_plugin_provenance: ToolPluginProvenance,
         auth: Option<&CodexAuth>,
+        elicitation_reviewer: Option<ElicitationReviewerHandle>,
     ) -> (Self, CancellationToken) {
         let cancel_token = CancellationToken::new();
         let mut clients = HashMap::new();
         let mut server_origins = HashMap::new();
         let mut join_set = JoinSet::new();
-        let elicitation_requests =
-            ElicitationRequestManager::new(approval_policy.value(), initial_permission_profile);
+        let elicitation_requests = ElicitationRequestManager::new(
+            approval_policy.value(),
+            initial_permission_profile,
+            elicitation_reviewer,
+        );
         let tool_plugin_provenance = Arc::new(tool_plugin_provenance);
         let startup_submit_id = submit_id.clone();
         let codex_apps_auth_provider = auth