/* UI-04-R1 skip-target offset (route-bound shell stylesheet; see lib/adapter.mjs SHELL_STYLES). The standard header is
   sticky and in flow directly above <main>, so <main> starts exactly at the header's bottom edge and the only scroll
   position at which the start of <main> (and the page heading) is not covered by the header is the document top.
   Activating the skip link scrolled <main> to the viewport's top edge, under the header. The header's height is not
   fixed: it is var(--ui-header-mobile) or var(--ui-header) at normal text but grows when its contents wrap (measured
   104.8px at 1366px with 200% text in WebKit), and CSS cannot read it. The viewport height is used as the upper bound
   of that height, so scrolling <main> into view always clamps to the document top. scroll-margin only affects where
   <main> is scrolled to: no layout box, spacing, colour or behaviour changes, and nothing is visible until it is used. */
.ui-main{scroll-margin-top:100vh}