- settings: playlists.materialize_path (separate root, mapped apart from the
music library so the media server never double-scans it) + materialize_mode
(symlink|copy).
- core/playlists/materialize.py: pure filesystem engine that (re)builds a
playlist folder of relative symlinks (or copies) into the real library —
idempotent, prunes stale entries, disambiguates filename collisions, never
escapes the root, and auto-falls-back to copy when the FS can't symlink.
No DB, no app state; ops injectable. 13 unit tests.
Isolated + additive — nothing live calls this yet (stitcher/trigger/routing
come next).
