test(browser): cover console.error with an error object

Claude-Session: https://claude.ai/code/session_01ShuAy8q8ZfPi8KHxwc8JpQ

test/browser/testdata/console-levels/index.html

@@ -9,6 +9,7 @@
     <div id="count">0</div>
     <script>
       console.error("boom from the page");
+      console.error(new Error("object arg detail"));
       console.warn("a warning");
       console.log("a plain log");
       console.debug("a debug line");