Reduce OpenAI WebView idle CPU

[jperezr21]

This reduces idle CPU usage from CodexBar’s offscreen OpenAI dashboard WKWebView cache.

• Stop loading and detach the cached WebView from its host window when hidden so WebKit can fully suspend background activity.
• Reattach the WebView when showing it for the next scrape.

[ratulsarna]

Thanks for the PR! Could we add a regression test that verifies this detach path (and the reattach path in show()) across release/reacquire, so we can catch any future drift in the idle-CPU behavior?