Design system structure

Makes every visual value in an Expo app come from one token file through one typed theme: semantic colour roles in light and dark palettes that are proven readable pair by pair, makeStyles and one AppText with type roles on the device pixel grid at every text size, the system font (bundled, pinned fonts as an opt-in), motion tokens with complete springs, and one press surface whose look is a token choice. Two checkers prove the theme equals the token file, the navigator and the root view follow it, and that no raw colour, size, weight, radius, duration, spring, palette import, platform shadow or second theme hides in the app's code.

Rules that must hold