UI component library

Gives an Expo app one shared component library in src/ui/: forty presentational components listed in a repo-owned catalogue (contracts/component-library.json), each sized from specs generated from the token file, pressed through the one press surface, showing every state with a cue beyond colour, named for VoiceOver and TalkBack, addressed by a required testID whose parts it derives itself, and proven by its own test. Two zero-dependency scripts prove the catalogue, the specs and the component rules, including the device lessons for iOS and Android.

Rules that must hold