fix(design-system): avoid hidden preview tab stops

Signed-off-by: Arjun Mahanti <arjun@squareup.com>

desktop-next/src/features/design-system/ui/GlassPage.tsx

@@ -18,7 +18,12 @@ function ChromePill() {
         <Tabs.Indicator />
       </Tabs.List>
       {items.map((label) => (
-        <Tabs.Panel key={label} value={label} className="bui-sr-only">
+        <Tabs.Panel
+          key={label}
+          value={label}
+          tabIndex={-1}
+          className="bui-sr-only"
+        >
           {label} surface selected in this material preview.
         </Tabs.Panel>
       ))}

desktop-next/tests/layout-refinements.spec.ts

@@ -70,6 +70,7 @@ test("Glass navigation shares selection motion and keyboard semantics", async ({
   await page.goto("/design/glass");
   const tabs = page.getByRole("tablist", { name: "Glass navigation preview" });
   const indicator = tabs.locator(".bui-tab-indicator");
+  await expect(page.getByRole("tabpanel")).toHaveAttribute("tabindex", "-1");
   await expect(
     tabs.getByRole("tab", { name: "Messages", exact: true }),
   ).toHaveAttribute("aria-selected", "true");