core: bundle GitLab auth plugin directly instead of dynamic install

Remove dynamic installation of built-in plugins. GitLab auth is now imported

directly as an internal plugin, eliminating network requests during startup

and simplifying the plugin loading logic.

Removes the need for test mocks since plugins are no longer

dynamically installed at runtime.

packages/opencode/src/config/config.ts

@@ -274,7 +274,7 @@ export namespace Config {
         ...(proxied() ? ["--no-cache"] : []),
       ],
       { cwd: dir },
-    ).catch(() => {})
+    )
   }
 
   async function isWritable(dir: string) {