Design system and app shell

Nothing can be built consistently until the tokens, the type scale and the shell exist. Every screen after this one assumes them.

Acceptance criteria

• Design tokens defined once, from the style guide, and nothing hardcodes a colour
• IBM Plex Sans loaded, weights 400 and 500 only
• Tabular figures applied to every element that renders a number
• Persistent header with the mark, the wordmark and three tabs: Setup, Guests, Plan
• Shared components exist and are used everywhere: button (primary, secondary, quiet), text field, select, tag pill, panel, slide-over
• No shadows anywhere
• Visible keyboard focus on every interactive element

Notes

Sits between TT-2 and everything else. Build it second and nothing after it needs retrofitting.