fix(google-auth): enable google antigravity auth by default (#66)

Make google_auth enabled by default (true) while still allowing users to disable it by setting google_auth: false.

🤖 Generated with assistance of OhMyOpenCode (https://github.com/code-yeongyu/oh-my-opencode)

src/index.ts

@@ -263,7 +263,7 @@ const OhMyOpenCodePlugin: Plugin = async (ctx) => {
   const callOmoAgent = createCallOmoAgent(ctx, backgroundManager);
   const lookAt = createLookAt(ctx);
 
-  const googleAuthHooks = pluginConfig.google_auth
+  const googleAuthHooks = pluginConfig.google_auth !== false
     ? await createGoogleAntigravityAuthPlugin(ctx)
     : null;