One shared download (input) folder feeds three separate library (output) folders —
the engine routes a finished download to the one matching its type, so YouTube never
lands in your real TV library (own Plex/Jellyfin library + agent). Replaces the single
transfer_path with movies_path / tv_path / youtube_path (legacy transfer_path migrates
into Movies on first read). Settings UI: shared Download folder + 🎬 Movies / 📺 TV /
▶️ YouTube library inputs. Tests updated incl. the migration. ruff + balance clean.