The S3b api.ts split introduced 5 exported-but-never-imported types
(PlaylistKind/PlaylistSource, DownloadJobKind, YT internal option/data shapes).
The publish gate's knip lane flagged them (my per-step checks ran tsc/eslint/
prettier/vitest but not knip). They're used inside their own modules by the
interfaces, so make them local (consumers compare against literals, never name
the type).