fix(advanced): use addArguments('-headless') — Options.headless() was removed in selenium-webdriver 4 (PER-8195)

CI's fresh npm install pulls selenium-webdriver 4.36 where firefox.Options().headless() no longer exists (TypeError: .headless is not a function), so the advanced spec never took a snapshot. Use addArguments('-headless'), matching the modern API.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Shivanshu-07

advanced/tests/todomvc_advanced.spec.js

@@ -19,7 +19,7 @@ describe('TodoMVC Advanced', function () {
     server = httpServer.createServer({ root: `${__dirname}/../..` });
     server.listen(PORT);
 
-    const options = new firefox.Options().headless();
+    const options = new firefox.Options().addArguments('-headless');
     if (process.env.FIREFOX_BINARY) options.setBinary(process.env.FIREFOX_BINARY);
 
     driver = await new Builder()