≤480px gets a hamburger button in the topbar and a fixed slide-out
panel from the right edge (width min(82vw, 320px)). The topbar keeps
only brand + tone toggle + hamburger visible; nav and the
header-right widgets (theme, lang, user menu, version meta) move
into the drawer.
Markup change: nav and .header-right are now wrapped in
.mobile-drawer, which is display:contents on desktop (no layout
effect) and a fixed translateX panel on mobile. The user-menu
dropdown chip hides on mobile and its links surface flat inside the
drawer.
JS: ~50 lines of vanilla. Tap hamburger / backdrop / ESC / swipe-
right-on-drawer all close. Clicking a nav link inside the drawer
closes it after the navigation kicks off so the panel doesn't linger
on the next page.
CSS: per-file @media block at the bottom of layout.css per the
agreed-upon organisation.
Giorgio Gilestro
2b3ea33884