Allow disabling plugin discovery prefetch at app-server startup (#57249)

## Why

Hosts that only need installed plugin inventory should be able to skip startup requests for plugin discovery.

## What changed

Add the stable, default-enabled `features.plugin_discovery_prefetch` flag. Setting it to `false` skips startup prefetching of the plugin directory, featured plugins, and recommendations while preserving installed plugin cache refreshes and bundle downloads.

## Testing

Update app-server integration coverage to verify that installed plugin bundles download with discovery prefetch disabled and that no directory, featured, or suggested plugin requests are made during startup. Also cover listing remote marketplaces with the flag disabled.

GitOrigin-RevId: 7cc3072f6045131b9f1acb851f6240db75ac173e

codex-rs/core-plugins/src/manager.rs

@@ -1588,6 +1588,7 @@ impl PluginsManager {
         self: &Arc<Self>,
         config: &PluginsConfigInput,
         auth: Option<CodexAuth>,
+        prefetch_recommendations: bool,
         on_effective_plugins_changed: Option<EffectivePluginsChangedCallback>,
     ) {
         self.maybe_start_remote_installed_plugins_cache_refresh_with_notify(
@@ -1598,6 +1599,9 @@ impl PluginsManager {
             EffectivePluginsChange::default(),
         );
 
+        if !prefetch_recommendations {
+            return;
+        }
         let manager = Arc::clone(self);
         let config = config.clone();
         tokio::spawn(async move {
@@ -1873,6 +1877,7 @@ impl PluginsManager {
         self.maybe_start_remote_plugin_caches_refresh(
             &context.global_config,
             auth.clone(),
+            /*prefetch_recommendations*/ true,
             on_effective_plugins_changed.clone(),
         );
         self.maybe_start_remote_installed_plugin_bundle_sync(
@@ -2874,6 +2879,7 @@ impl PluginsManager {
     pub fn maybe_start_plugin_startup_tasks_for_config(
         self: &Arc<Self>,
         config: &PluginsConfigInput,
+        prefetch_discovery: bool,
         reload_config: ConfigLayerReload,
         on_effective_plugins_changed: Option<EffectivePluginsChangedCallback>,
         upgrade_warnings: mpsc::UnboundedSender<String>,
@@ -2966,6 +2972,7 @@ impl PluginsManager {
                 manager.maybe_start_remote_plugin_caches_refresh(
                     &config_for_remote_sync,
                     auth.clone(),
+                    prefetch_discovery,
                     on_effective_plugins_changed.clone(),
                 );
                 manager.maybe_start_remote_installed_plugin_bundle_sync(
@@ -2973,6 +2980,9 @@ impl PluginsManager {
                     auth.clone(),
                     on_effective_plugins_changed,
                 );
+                if !prefetch_discovery {
+                    return;
+                }
                 let mut scopes = crate::remote::cached_remote_plugin_catalog_scopes(
                     manager.codex_home.as_path(),
                     &remote_plugin_service_config(&config_for_remote_sync),
@@ -2985,18 +2995,12 @@ impl PluginsManager {
                 }
                 manager.maybe_start_remote_catalog_cache_refresh(
                     &config_for_remote_sync,
-                    auth,
+                    auth.clone(),
                     scopes,
                     RemoteCatalogCacheRefreshMode::Force,
                 );
-            });
-
-            let config_for_featured_plugins = config.clone();
-            let manager = Arc::clone(self);
-            tokio::spawn(async move {
-                let auth = manager.auth_manager.auth().await;
                 if let Err(err) = manager
-                    .featured_plugin_ids_for_config(&config_for_featured_plugins, auth.as_ref())
+                    .featured_plugin_ids_for_config(&config_for_remote_sync, auth.as_ref())
                     .await
                 {
                     warn!(

codex-rs/core-plugins/src/manager_tests.rs

@@ -6147,6 +6147,7 @@ plugins = true
     manager.maybe_start_remote_plugin_caches_refresh(
         &config,
         Some(auth.clone()),
+        /*prefetch_recommendations*/ true,
         /*on_effective_plugins_changed*/ None,
     );