Centralize app enabled-state evaluation (#36916)

## What changed

- Add `AppToolPolicyEvaluator::apply_app_enabled_state` and use it when
  presenting app lists, building plugin context, and deciding whether app
  instructions are available.
- Preserve each app's source state unless local or managed configuration
  explicitly overrides it.
- Keep connector discovery and post-install refresh checks based on raw
  accessibility rather than configured enablement.

## Testing

- Cover default enablement, per-app overrides, managed disablement, and
  preservation of unconfigured source state.

GitOrigin-RevId: f1a62d55e7cc48b37113848e3baa0d69d8d9c8a8

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

@@ -71,6 +71,7 @@ use codex_analytics::InvocationType;
 use codex_analytics::TurnResolvedConfigFact;
 use codex_analytics::build_track_events_context;
 use codex_async_utils::OrCancelExt;
+use codex_connectors::AppToolPolicyEvaluator;
 use codex_core_plugins::RecommendedPluginCandidatesInput;
 use codex_core_skills::injection::InjectedHostSkillPrompts;
 use codex_extension_api::ExtensionData;
@@ -754,7 +755,8 @@ async fn build_skills_and_plugins(
                 .map(|connector_id| connector_id.0.clone()),
             connectors::accessible_connectors_from_mcp_tools(mcp_tools),
         );
-        connectors::with_app_enabled_state(connectors, &turn_context.config)
+        AppToolPolicyEvaluator::new(&turn_context.config.config_layer_stack)
+            .apply_app_enabled_state(connectors)
     } else {
         Vec::new()
     };
@@ -1476,21 +1478,6 @@ pub(crate) async fn built_tools(
     let apps_enabled = turn_context.apps_enabled();
     let accessible_connectors =
         apps_enabled.then(|| connectors::accessible_connectors_from_mcp_tools(all_mcp_tools));
-    let connectors = if apps_enabled {
-        let connectors = codex_connectors::merge::merge_plugin_connectors_with_accessible(
-            connector_snapshot
-                .connector_ids()
-                .iter()
-                .map(|connector_id| connector_id.0.clone()),
-            accessible_connectors.clone().unwrap_or_default(),
-        );
-        Some(connectors::with_app_enabled_state(
-            connectors,
-            &turn_context.config,
-        ))
-    } else {
-        None
-    };
     let tool_suggest_is_enabled = tool_suggest_enabled(turn_context);
     let PreparedToolRecommendations {
         auth,
@@ -1510,7 +1497,7 @@ pub(crate) async fn built_tools(
                 .collect::<Vec<_>>();
             async {
                 if apps_enabled && tool_suggest_is_enabled {
-                    if let Some(accessible_connectors) = connectors.as_ref() {
+                    if let Some(accessible_connectors) = accessible_connectors.as_ref() {
                         match connectors::list_tool_suggest_discoverable_tools_with_auth(
                             &turn_context.config,
                             sess.services.plugins_manager.as_ref(),