챕터를 유지하는 비공개 출력
- Reads stored chapters, primary audio properties, duration, codec, sample rate, channel layout, and cover-art presence.
- Rejects missing, zero-length, overlapping, out-of-order, out-of-bounds, encrypted, malformed, and non-audio chapter sources.
- Creates private CSV and JSON manifests with normalized timing and bounded warnings.
- Uses neutral chapter-0001 names. Titles never enter URLs, logs, analytics, ZIP entry names, or download filenames.
- Does not accept remote URLs, playlists, user timestamps, chapter edits, archives, or custom FFmpeg switches.
Results are private, served with no-store headers, retained only for the existing download window, and then cleaned up automatically.