Surface a horizontal "Continue reading" shelf at the top of the homepage,
fed by the user's read-progress history. Each card jumps back to the exact
page they left off (deep-linking `?page=N` past the first) and flags how
many chapters have landed since — the personal new_chapters_count from the
read-progress list. The shelf is fetched after the catalogue load so the
public browse path stays unauthenticated; guests get an empty list (401
swallowed) and the shelf stays hidden.
Add new_chapters_count to the frontend ReadProgressSummary type to match
the backend. Component unit tests cover href/deep-link, badge visibility,
and the no-chapter fallback; e2e covers signed-in (shelf + badge) and
anonymous (hidden).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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