primer/primitives ? reverse-engineered prompt

Build me a small design tokens package for Primer that ships color, spacing, typography, size, and motion values in JSON and turns them into CSS variables people can import in their apps.

I want light and dark themes, plus the accessibility variants like high contrast, colorblind, and tritanopia, and I want the token setup to support overrides so each mode can reuse the base values and only change what’s different. Please also make it easy to generate the published files from the token source, and include a simple Storybook or docs page that shows how to use the imports and CSS variables in real components.

If anything is unclear, check the current docs online and make sensible choices. Keep it friendly for people using GitHub’s design system, and make sure the package is ready to publish to npm.