perf(playout): parallelize playlist validation with dedup and worker pool

.github/instructions/DONE.md

@@ -2,6 +2,14 @@
 
 > Completed tasks from [TODO](./TODO.md). Product, feature, and release history lives in [CHANGELOG](./CHANGELOG.md); this file keeps only engineering and ops notes not captured there.
 
+## Playout startup performance (2026-08-16)
+
+- Parallelized playlist validation: dedup repeated paths, probe unique files concurrently (`PLAYOUT_VALIDATE_WORKERS` default `runtime.NumCPU()`), run the two `ffprobe` probes concurrently, and validate once in `main()` (removed the redundant `-validate` pre-step in `start-playout.sh`). See CHANGELOG.
+
+## Cloudflare Workers frontend URLs (2026-08-16)
+
+- Viewer `main.ts` uses `VITE_PUBLIC_APP_URL` for all API requests and `VITE_PUBLIC_WS_URL` for WebSocket connections so the Workers-served SPA reaches the app origin cross-origin. See CHANGELOG.
+
 ## Test infrastructure & refactors (2026-08-07)
 
 - Chat service `main.go` split into 8 packages (config, auth, db, handlers, ws, media, ratelimit, metrics); `db.RedisClient` + `db.PubSub` interfaces added for mocking.