docs: reorganize TODO, DONE, and BACKLOG task tracking

.github/instructions/BACKLOG.md

@@ -2,16 +2,6 @@
 
 > All current work is planned in [TODO](./TODO.md) (2026-08-13). This file lists backlog items; new unplanned work is added here.
 
-## Chat improvements (remaining)
-
-- [ ] Manual smoke: viewer join/leave shows a 3s flash (not a chat row); reconnect <5s shows no duplicate; admin chat-log table has no system rows
-
-## Playout improvements (remaining)
-
-- [ ] Test in Firefox: live playback, rebuffer/recovery, chat sync; record quirks in `docs/STREAMING.md`
-- [ ] Rebuild + run playout; confirm `playlist.m3u8` lists ~12 segments at 2s each
-- [ ] Manual: verify viewer latency and cache-hit behavior after the change
-
 ## Setup phases remaining
 
 ### Phase 5: complete manual Cloudflare and external-service setup
@@ -91,28 +81,6 @@
 - [ ] UptimeRobot: add keyword monitor for `https://linearvoid.tv/hls/playlist.m3u8` (keyword: `#EXTM3U`, 5min)
 - [ ] Alert on 2 consecutive failures, notify via email + Discord/Slack webhook
 
-## Frontend Tests
-
-### User Frontend
-
-- [ ] Test coverage for all critical frontend components and interactions
-- [ ] Add code coverage reporting and enforce minimum coverage threshold in CI/CD pipeline
-- [ ] Document test cases and expected outcomes
-
-### Admin Frontend
-
-- [ ] Test coverage for all critical admin UI components and interactions
-- [ ] Add code coverage reporting and enforce minimum coverage threshold in CI/CD pipeline
-- [ ] Document test cases and expected outcomes
-
-## Backend Integration Tests
-
-### Cloudflare R2
-
-- [ ] Test retrieval of segments and manifests from R2 via Cloudflare edge
-- [ ] Validate cache hit/miss behavior and performance metrics
-- [ ] Validate edge cache hit/miss behavior with repeat requests — script `scripts/validate-edge-cache.sh` created
-
 ## External Services
 
 > Evidence tracker: `docs/operations/cloudflare-uptimerobot-checklist.md`