materialize_playlist_from_batch(batch, download_tasks, config) collects the real
on-disk path of every resolved track from the batch's OWN payload — owned via
analysis_results.matched_file_path, downloaded via tasks.final_file_path — runs
each through the playback path resolver (Docker-correct), de-dupes, and hands the
list to rebuild_playlist_folder. Gated on playlist_folder_mode.
No re-matching, no source IDs, no mirrored-playlist lookup — works for any
organize-by-playlist download including the all-owned case. 5 tests. Still
isolated; the triggers wire it in next.
