Added: below 640 px sidebars behave as modal drawers (overlay, scrim,
Android Back). Fixed: split-pane Back/Forward stay with the focused pane;
PDF highlights offer Copy ref and Linked references; empty search tabs;
future-dated journals no longer displace today; mobile fold controls stop
stealing text taps; bare `/` defaults to page reference; page/tag
completion uses OG's adaptive ordering.
