AppSidebar (icon-collapsible, sync warning badge, brand header),
NavUser footer (avatar + privacy/theme/logout dropdown), and a thin
header with SidebarTrigger, breadcrumbs, and quick toggles. Mobile
drawer and cmd+B come from the sidebar primitives.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>