Function toggle_devtools 

pub fn toggle_devtools(
    state: &Arc<AppState>,
    args: &Value,
) -> Result<Value, String>

Toggle DevTools for the main window.

Uses CEF’s native show_dev_tools() API, which triggers BrowserViewDelegate::on_popup_browser_view_created with is_devtools=1. That callback creates a top-level CefWindow with a native title bar, producing a standalone DevTools window — identical to Tauri’s open_devtools().