Bookshelf

Bookshelf is the offline-storage primitive — file type / mimetype / size / blob. Holds any content type (books, audio, video, games, voicemail, podcasts, documents, RSS articles). Specialized Minis (book reader, podcast player, voicemail, etc.) USE this primitive — they're the players; this is the shelf. Per project_bookshelf_is_storage_primitive.md.