[codex] Skip local curated discovery for remote plugins (#27311)

## Summary

- skip the local `openai-curated` marketplace before marketplace loading
when tool-suggest discovery uses remote plugins
- preserve existing marketplace listing behavior for all other callers
and when remote plugins are disabled
- add regression coverage proving the curated marketplace is excluded
before its malformed manifest can be read

## Why

Tool-suggest discovery previously loaded every local `openai-curated`
plugin manifest and only discarded that marketplace afterward when
remote plugins were enabled. The remote catalog is used in that mode, so
the local scan consumed CPU without contributing discoverable plugins.

## Impact

Remote-plugin tool suggestion discovery no longer reads the local
curated marketplace and its plugin manifests. `openai-bundled`,
configured marketplaces, normal `plugin/list` behavior, and local
curated discovery when remote plugins are disabled are unchanged.

## Validation

- `just test -p codex-core-plugins
list_marketplaces_can_skip_openai_curated_before_loading`
- `just test -p codex-core
list_tool_suggest_discoverable_plugins_omits_openai_curated_when_remote_enabled`
- `just fmt`
- `git diff --check`

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

@@ -87,7 +87,11 @@ impl PluginsManager {
         }
 
         let marketplaces = self
-            .list_marketplaces_for_config(&input.plugins, &[])
+            .list_marketplaces_for_config(
+                &input.plugins,
+                &[],
+                /*include_openai_curated*/ !input.plugins.remote_plugin_enabled,
+            )
             .context("failed to list plugin marketplaces for tool suggestions")?
             .marketplaces;
         let mut installed_app_connector_ids = self
@@ -110,11 +114,6 @@ impl PluginsManager {
         let mut discoverable_plugins = Vec::<ToolSuggestDiscoverablePlugin>::new();
         for marketplace in marketplaces {
             let marketplace_name = marketplace.name;
-            if input.plugins.remote_plugin_enabled
-                && marketplace_name == OPENAI_CURATED_MARKETPLACE_NAME
-            {
-                continue;
-            }
             let use_legacy_local_curated_filter = should_use_legacy_local_curated_discovery_filter(
                 &marketplace_name,
                 marketplace.path.as_path(),