feat: support remote_sync for plugin install/uninstall. (#14878)

- Added forceRemoteSync to plugin/install and plugin/uninstall.
- With forceRemoteSync=true, we update the remote plugin status first,
then apply the local change only if the backend call succeeds.
- Kept plugin/list(forceRemoteSync=true) as the main recon path, and for
now it treats remote enabled=false as uninstall. We
will eventually migrate to plugin/installed for more precise state
handling.

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

@@ -3,6 +3,7 @@ mod injection;
 mod manager;
 mod manifest;
 mod marketplace;
+mod remote;
 mod render;
 mod store;
 mod toggles;