ScanPodcastFolder walks a podcasts-typed media folder, treating each
subdirectory as a podcast show and each audio file inside as an
episode. Writes media_items.type='podcast' + episodes rows + media_files
rows. RSS-subscribed feeds (podcast_feeds table) arrive in sub-plan 5;
this task covers filesystem-only ingestion.
ScanFolder dispatches to this path when folder.Type='podcasts'.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
