Press `?` in the reader to open a Sheet documenting the existing bindings
(arrows/J/K paging, Home/End, chapter nav, Esc); Esc or the close button
dismisses it. While open, the reader swallows navigation keys so paging
can't happen behind the overlay. e2e covers open-on-? and close-on-Esc.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
