feat: refactor on openai-curated plugins. (#14427)

- Curated repo sync now uses GitHub HTTP, not local git.
- Curated plugin cache/versioning now uses commit SHA instead of local.
- Startup sync now always repairs or refreshes curated plugin cache from
tmp (auto update to the lastest)

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

@@ -7,6 +7,7 @@ mod render;
 mod store;
 
 pub(crate) use curated_repo::curated_plugins_repo_path;
+pub(crate) use curated_repo::read_curated_plugins_sha;
 pub(crate) use curated_repo::sync_openai_plugins_repo;
 pub(crate) use injection::build_plugin_injections;
 pub use manager::AppConnectorId;