- mpv: --force-media-title '<podcast> — <episode>' so macOS Now Playing shows
the podcast name instead of the download-hash filename (mediaTitle PlayOption)
- media registry: artist is now the human podcast title (customName ||
podcast.title), falling back to podcastId
- downloads: write the podcast cover as a <base>.jpg sibling so mpv's
cover-art-auto=exact picks it up for artwork; delete it with the download
