new opt-in feature — default keeps everything, so nothing changes unless a channel sets it.
- history got smarter: youtube rows now carry channel_id + published_at (mined from
search_ctx) + a pruned_at marker. new queries: youtube_channels_with_downloads,
youtube_channel_episodes, mark_download_pruned.
- core/video/retention.py (pure): parse_retention + episodes_to_prune — age by UPLOAD
date (published_at, filename fallback); 'count_N' keeps newest N, 'days_N' keeps last N
days; undated episodes never pruned.
- handler auto_video_clean_youtube_episodes: for each channel with a policy, delete the
out-of-window video + its -thumb/.nfo sidecars (only the exact recorded dest_path, never
walks folders), then mark the history row pruned — KEPT so the scan never re-downloads it.
- 'Keep' dropdown in each channel's cog modal (Everything / Last 30 episodes / Last 3 / 6
months); playlists excluded. seeded daily automation + register/block/label/icon/sort.
pure math + handler (i/o injected) + the prune-keeps-dedup DB contract all tested.
