fix(ui): center desktop navbar menus

packages/ui/test/ui.test.ts

@@ -3135,6 +3135,8 @@ test("navbar uses a valid aria-current and takes roving focus on its menu", asyn
    */
   expect(source).not.toContain("? 'page' : ''");
   expect(source).toContain("data-wrn-roving");
+  expect(source).toContain("left: 50%;");
+  expect(source).toContain("transform: translateX(-50%);");
 
   const html = await renderComponent(source, {
     label: "Main",