fix(ui): avoid layout shifts in overflow-menu and repo filter (#37818)

Eliminate two layout shifts in the menu, one related to non-existant
label on page load and one to `0` value rendering.

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>
Co-authored-by: bircni <bircni@icloud.com>

web_src/js/webcomponents/overflow-menu.ts

@@ -213,6 +213,7 @@ window.customElements.define('overflow-menu', class extends HTMLElement {
         if (newWidth !== this.lastWidth) {
           requestAnimationFrame(() => {
             this.updateItems();
+            this.setAttribute('data-ready', ''); // reveal via CSS [data-ready]
           });
           this.lastWidth = newWidth;
         }