chore: initial scaffold of KDC Design System

Initial repository scaffold:
- design.md (google-labs-code/design.md format) as canonical token + guidelines source
- brand assets, foundations, tokens (W3C-style JSON)
- 12 component primitives, each with labeled anatomy.svg and spec README
- light / dark / high-contrast themes, web/mobile/email/print/presentation templates
- docs (getting started, principles, a11y, voice & tone, contributing)
- runnable web example, token build script stub, CI placeholder

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/contributing/README.md

@@ -0,0 +1,16 @@
+# Contributing
+
+1. Open an issue describing the proposed change (token, component, doc).
+2. Branch from `main`: `git checkout -b feat/<short-name>`.
+3. Update `design.md` first — it is the source of truth.
+4. Regenerate `tokens/` exports.
+5. Add or update component documentation under `components/<name>/`.
+6. Open a PR; the design-system maintainers (see `CODEOWNERS`) will review.
+
+## PR checklist
+
+- [ ] `design.md` updated
+- [ ] Tokens regenerated
+- [ ] Component spec updated (states + a11y)
+- [ ] Changelog entry added under `[Unreleased]`
+- [ ] Visual examples attached