MC-4893

## Goal Scheduled retention for the cloud outputs tree. Radio mp3s in `PKA-Outputs/radio/` older than 90 days → delete. `board/`, `study/`, `reports/` → KEEP FOREVER (never prune). Per the architecture decision (board/study forever, mp3 90d). ## Design - A small Luci script + scheduler task (daily). Resolve dir via `python3 ~/workspace/PKA/pka_paths.py outputs-dir radio`. - Delete radio mp3 (+ its sidecar manifest/seed/summary with the same date) older than 90 days, by date-in-filename (preferred) else mtime. - DRY-RUN mode that logs exactly what it WOULD delete; live mode deletes. Idempotent. Manifest-aware. - SAFETY: never touch board/study/reports; and keep at least the most recent ~10 radio episodes regardless of age (avoid emptying radio). ## Constraints - Only radio/. Atomic. Log every deletion. No system cron — use the Luci scheduler (`~/workspace/tasks/`). ## Verification: dry-run lists correct >90d radio candidates; live run removes only those; board/study/reports untouched; recent N kept. ## Terminal-state report REQUIRED.