test(frontend): cover the lifecycle, the voice and the repaints

Component and store cases for everything in this series, several of
which exist because the thing they pin is invisible everywhere else:

- `view-lifecycle` and `keyboard-reach` — a document listener count
  that does not grow across a simulated navigate cycle, and a tab
  sequence that reaches the sidebar and plays a row without a mouse.
- `notifications`, `notification-store`, `confirm-dialog`,
  `empty-states` — the four levels, the (level, region, key)
  coalescing window, and loading/failed/empty as three states.
- `card-grid-repaint` — fails if `artists-view`'s or `genres-view`'s
  per-render arrow functions are hoisted to stable fields, which is
  the audit's own recommendation and takes the cards from 1 highlighted
  to 0. It exists for no other reason.
- `lazy-track-details` — reads the five sources and fails on a
  returning static import, the same shape as `TestNoDirectRuntimeEmits`
  and for the same reason: the invariant is about what the code does
  *not* say.
- `now-playing` — a position report that changes nothing must not
  touch the DOM again, and a track change must. The first fails
  against the old unconditional `updated()`.
- `playlist-virtualization`, `list-render-cost`, `selection`, `icons`,
  and the store cases for the library-filter race, the never-settling
  waiter and the per-playlist patch.

frontend/test/components/chrome.test.ts

@@ -25,7 +25,9 @@ describe('<app-sidebar>', () => {
     const el = await fixture('app-sidebar');
 
     expect(
-      shadowAll(el, 'li').map((li) => li.getAttribute('data-testid')),
+      shadowAll(el, 'li button').map((item) =>
+        item.getAttribute('data-testid'),
+      ),
     ).toEqual([
       'nav-home',
       'nav-playlists',
@@ -44,8 +46,8 @@ describe('<app-sidebar>', () => {
   it('marks exactly one item as the current page', async () => {
     const el = await fixture('app-sidebar');
 
-    const current = shadowAll(el, 'li').filter(
-      (li) => li.getAttribute('aria-current') === 'page',
+    const current = shadowAll(el, 'li button').filter(
+      (item) => item.getAttribute('aria-current') === 'page',
     );
 
     expect(current).toHaveLength(1);