feat: Phase 2+3 frontend coverage — responsive + accessibility tests + CI threshold

- Viewer accessibility: 5 tests (aria-labels, aria-expanded, label association, alert role)
- Viewer responsive: 3 tests (chat-collapsed, CSS grid, now-playing aria-live)
- Admin accessibility: 3 tests (nav aria-label, aria-current, focusability)
- Admin responsive: 2 tests (tab visibility, essential tabs)
- Coverage: vitest v8 provider, 40% stmt/lines, 30% branches/funcs
- CI: test:coverage step between lint and build
- Total: 44 frontend tests (31 + 13 new)
- Updated TODO.md (Phase 2+3 done), DONE.md, MEMORY.md

.github/instructions/TODO.md

@@ -10,17 +10,17 @@
   - [x] Create playlist fixtures for empty, comment-only, mixed-validity, and valid playlists
   - [x] Document the ffmpeg fixture-generation commands in the relevant test headers
 
-- [ ] Phase 2: finish frontend coverage for the live viewer experience
+- [x] Phase 2: finish frontend coverage for the live viewer experience
   - [x] Add tests for HLS player startup, manifest resolution, and cross-origin/local fallback behavior
   - [x] Add tests for chat send/receive, presence updates, private DM flow, and reconnect behavior
-  - [ ] Add responsive-layout and accessibility checks for the viewer shell and chat sidebar
-  - [ ] Add coverage reporting and enforce a minimum threshold in CI
+  - [x] Add responsive-layout and accessibility checks for the viewer shell and chat sidebar
+  - [x] Add coverage reporting and enforce a minimum threshold in CI
 
-- [ ] Phase 3: finish admin frontend coverage
+- [x] Phase 3: finish admin frontend coverage
   - [x] Add tests for playlist management, moderation flows, and dashboard rendering
   - [x] Add tests for API integration points with mocked backend responses
-  - [ ] Add responsive-layout and accessibility checks for admin screens
-  - [ ] Add coverage reporting and enforce a minimum threshold in CI
+  - [x] Add responsive-layout and accessibility checks for admin screens
+  - [x] Add coverage reporting and enforce a minimum threshold in CI
 
 - [x] Phase 4: validate the R2 and edge-delivery path
   - [x] Add an integration test for upload and retrieval of HLS objects through the R2 path