On phones the lightbox caption and "Read the story" button were pinned to the
screen bottom, cramped and overlapped by the floating "Ask MSOS" pill
(z-index above the lightbox). Now:
- lightbox becomes a centred column on <=600px: image -> button -> caption
flow directly under the photo instead of being absolutely bottom-pinned;
- image capped at 62vh so tall/portrait photos leave room for the button;
- the Ask-MSOS pill is hidden while the viewer is open (body.lightbox-open),
so it can no longer overlap the controls.
Desktop layout is unchanged.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>