shadcn/ui

Replace the :root / .dark blocks in your globals.css with shadcn/globals.css, after @import "tailwindcss".

shadcn variable	Atomus token
--background, --card, --popover	bg-primary
--foreground	text-primary
--primary / --primary-foreground	bg-brand-solid / text-on-brand
--secondary	bg-secondary
--muted / --muted-foreground	bg-tertiary / text-tertiary
--accent / --accent-foreground	bg-brand-subtle / text-brand
--destructive	bg-error-solid
--border / --input / --ring	border-secondary / border-primary / border-focus
--chart-1 … 5	brand 600, 400, 200, gray 400, 200
--sidebar-*	sidebar surfaces and accents
--radius	radius-lg

Brand, theme and radius modes keep working: shadcn components follow data-brand, data-theme and data-radius.