responsive states

DashboardShell has two breakpoints: ≥1280 (full 4-cell grid) and <1280 (stacked: topnav over stage; brand + sidenav hide). below 768 the topnav padding tightens to match smaller viewports.

when the brand corner and sidenav hide, apps should put a hamburger button in the topnav and render their own drawer for the nav contents. consumers own that — the shell stays dumb.