Add `new_chapters_count` to each `GET /me/read-progress` item: how many
chapters sit past the reader's last-read chapter, computed by a correlated
subquery on chapter number. It is 0 when the reader is caught up, and 0
when the last-read chapter is unknown (manga-level progress or a deleted
chapter) so we never over-claim. (manga_id, number) is non-unique, so this
counts positions past the reader rather than distinct files.
Backs the personal "new since last read" indicator on the upcoming
Continue-reading shelf. Tests cover the mid-series, caught-up, and
no-read-chapter cases.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
f318c3bf51