Purpose:
This package provides typed design tokens (raw + semantic) for Headless.
It is pure Dart and must stay usable without Flutter.

Non-goals:
- No runtime JSON parsing of W3C tokens.
- No UI widgets, no theming implementations.

Invariants:
- Do not import Flutter packages here.
- Raw tokens are a generated source of truth (tooling step).
- Semantic tokens are a stable API surface; changes are additive in minor.

Correct usage:
- Import `package:headless_tokens/headless_tokens.dart` and use typed token APIs.

Anti-patterns:
- Adding `package:flutter/*` dependencies.
- Adding widget/state logic into tokens.

