[codex] Enable remote plugins by default (#30297)

## Summary

- enable the remote plugin feature by default
- promote the remote plugin feature from under development to stable
- preserve the existing `features.remote_plugin` override for explicitly
disabling it
- keep legacy disabled-path coverage explicit in TUI and app-server
tests

## Impact

Remote plugin functionality is enabled by default for configurations
that do not set the feature flag. The existing Codex backend
authentication gate still applies.

## Validation

- `just fmt`
- `just test -p codex-features`
- `just test -p codex-tui
plugins_popup_remote_section_fallback_states_snapshot`
- targeted `codex-app-server` plugin-list and skills-list tests
- `git diff --check`

The full TUI and app-server suites were also exercised locally. All
remote-plugin-related coverage passed; unrelated local
sandbox/test-binary failures remain outside this change.

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

@@ -37,6 +37,13 @@ use wiremock::matchers::query_param;
 #[tokio::test]
 async fn returns_fallback_plugins_when_remote_disabled_for_codex_auth() {
     let codex_home = tempdir().expect("tempdir should succeed");
+    write_file(
+        &codex_home.path().join(CONFIG_TOML_FILE),
+        r#"[features]
+plugins = true
+remote_plugin = false
+"#,
+    );
     let curated_root = curated_plugins_repo_path(codex_home.path());
     write_openai_curated_marketplace(&curated_root, &["sample", "slack", "openai-developers"]);
 
@@ -69,8 +76,7 @@ async fn returns_api_curated_fallback_plugins_for_direct_provider_auth() {
     let curated_root = curated_plugins_repo_path(codex_home.path());
     write_openai_api_curated_marketplace(&curated_root, &["sample", "slack", "openai-developers"]);
 
-    let mut plugins = load_plugins_config(codex_home.path(), codex_home.path()).await;
-    plugins.remote_plugin_enabled = true;
+    let plugins = load_plugins_config(codex_home.path(), codex_home.path()).await;
     let plugins_manager = PluginsManager::new(codex_home.path().to_path_buf());
     plugins_manager.set_auth_mode(Some(AuthMode::ApiKey));
     let auth = CodexAuth::from_api_key("test-api-key");
@@ -153,7 +159,6 @@ async fn omits_openai_curated_but_keeps_configured_marketplaces_for_remote_codex
         &format!(
             r#"[features]
 plugins = true
-remote_plugin = true
 
 [marketplaces.{bundled_marketplace_name}]
 source_type = "git"
@@ -188,8 +193,7 @@ async fn includes_openai_curated_when_remote_enabled_without_auth() {
     let curated_root = curated_plugins_repo_path(codex_home.path());
     write_openai_curated_marketplace(&curated_root, &["slack"]);
 
-    let mut plugins = load_plugins_config(codex_home.path(), codex_home.path()).await;
-    plugins.remote_plugin_enabled = true;
+    let plugins = load_plugins_config(codex_home.path(), codex_home.path()).await;
     let plugins_manager = PluginsManager::new(codex_home.path().to_path_buf());
     let discoverable_plugins = list_discoverable_plugins(
         &plugins_manager,
@@ -788,7 +792,6 @@ async fn expands_cached_remote_plugins_by_loaded_apps() {
         &codex_home.path().join(CONFIG_TOML_FILE),
         r#"[features]
 plugins = true
-remote_plugin = true
 "#,
     );
 

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

@@ -1062,7 +1062,6 @@ async fn remote_installed_cache_ignores_plugins_missing_local_cache() {
         &codex_home.path().join(CONFIG_TOML_FILE),
         r#"[features]
 plugins = true
-remote_plugin = true
 "#,
     );
 
@@ -1296,7 +1295,6 @@ async fn remote_global_catalog_ignores_local_curated_plugins() {
         &codex_home.path().join(CONFIG_TOML_FILE),
         r#"[features]
 plugins = true
-remote_plugin = true
 
 [plugins."linear@openai-curated"]
 enabled = true
@@ -1347,7 +1345,6 @@ async fn remote_plugin_feature_keeps_local_curated_without_codex_backend() {
         &codex_home.path().join(CONFIG_TOML_FILE),
         r#"[features]
 plugins = true
-remote_plugin = true
 
 [plugins."linear@openai-curated"]
 enabled = true
@@ -4878,7 +4875,6 @@ async fn remote_plugin_caches_refresh_warms_recommended_plugins_cache() {
         &tmp.path().join(CONFIG_TOML_FILE),
         r#"[features]
 plugins = true
-remote_plugin = true
 "#,
     );
 
@@ -4939,7 +4935,6 @@ async fn recommended_plugins_mode_deduplicates_concurrent_cache_misses() {
         &tmp.path().join(CONFIG_TOML_FILE),
         r#"[features]
 plugins = true
-remote_plugin = true
 "#,
     );
 
@@ -5017,7 +5012,6 @@ async fn recommended_plugin_candidates_filter_installed_and_disabled_plugins() {
         &tmp.path().join(CONFIG_TOML_FILE),
         r#"[features]
 plugins = true
-remote_plugin = true
 "#,
     );
     let server = MockServer::start().await;
@@ -5090,7 +5084,6 @@ async fn recommended_plugins_mode_caches_explicit_false() {
         &tmp.path().join(CONFIG_TOML_FILE),
         r#"[features]
 plugins = true
-remote_plugin = true
 "#,
     );
 
@@ -5130,7 +5123,6 @@ async fn recommended_plugins_mode_retries_after_fetch_failure() {
         &tmp.path().join(CONFIG_TOML_FILE),
         r#"[features]
 plugins = true
-remote_plugin = true
 "#,
     );
 

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

@@ -149,7 +149,7 @@ pub(crate) async fn load_plugins_config(codex_home: &Path, cwd: &Path) -> Plugin
         feature_enabled(
             &effective_config,
             "remote_plugin",
-            /*default_enabled*/ false,
+            /*default_enabled*/ true,
         ),
         "https://chatgpt.com/backend-api/".to_string(),
     )