fix(admin): remove spurious scrollbar from feedback tab strip

Marc reported a stray "mini scroll-button" on the right side of the
admin feedback inbox tab strip (Open / Acknowledged / Resolved /
Archived). The four short tabs do not horizontally overflow the
viewport, so the painted bar surprised him every time he opened the
inbox.

Root cause is a CSS overflow coupling: setting only `overflow-x: auto`
silently forces `overflow-y` to `auto` too, because a single axis
cannot be `visible` while the other clips. The strip is locked at
`h-9` (36 CSS px) but its badge children (`py-0.5` + text-xs digits)
ride 1-2 px taller than the strip on some glyph stacks, so the
implicit `overflow-y: auto` paints a tiny vertical scrollbar on the
right edge.

Fix is a single class on `tabsListVariants`: `overflow-y-hidden`
(plus `overflow-y-visible` in the vertical-orientation override so
vertical tab columns are not affected). Horizontal swipe and
keyboard-arrow scrolling still work — only the implicit y-axis bar
is suppressed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/ui/__tests__/tabs.test.tsx

@@ -0,0 +1,33 @@
+import { describe, expect, it } from "vitest";
+import { renderToStaticMarkup } from "react-dom/server";
+
+import { Tabs, TabsList, TabsTrigger } from "../tabs";
+
+describe("<TabsList>", () => {
+  it("clamps the y-axis so a fixed-height strip never paints a vertical scrollbar", () => {
+    // Marc reported a stray "mini scroll-button" on the right side of
+    // the feedback inbox tab strip (Open / Acknowledged / Resolved /
+    // Archived). Root cause: `overflow-x-auto` couples to `overflow-y`
+    // — once one axis is `auto`, the other can no longer be `visible`,
+    // so the browser silently flips it to `auto` too. Combined with
+    // the fixed `h-9` strip and the badges (`py-0.5` + text-xs) that
+    // ride 1-2 px taller than the strip on some glyph stacks, a
+    // tiny vertical scrollbar paints on the right edge.
+    //
+    // Locking `overflow-y-hidden` on the strip kills the painted bar
+    // without touching the horizontal swipe behaviour.
+    const html = renderToStaticMarkup(
+      <Tabs defaultValue="a">
+        <TabsList>
+          <TabsTrigger value="a">A</TabsTrigger>
+          <TabsTrigger value="b">B</TabsTrigger>
+        </TabsList>
+      </Tabs>,
+    );
+    const list = html.match(/<div\b[^>]*data-slot="tabs-list"[^>]*>/);
+    expect(list).not.toBeNull();
+    expect(list![0]).toMatch(/\boverflow-y-hidden\b/);
+    // Horizontal scroll behaviour is still intact for long strips.
+    expect(list![0]).toMatch(/\boverflow-x-auto\b/);
+  });
+});