Add workflow infrastructure — ESLint, Prettier, Husky, Vitest, 7 new skills

Phase 1: Session log archived (1096→91 lines), D031 token access convention
Phase 2: ESLint v9 + Prettier + jsx-a11y, initial config and lint fixes
Phase 3: 7 new skills (polish, harden, normalize, clarify, typeset, quieter, adapt)
         + Vercel reference docs, updated audit/review-component refs
Phase 4: Husky + lint-staged pre-commit hooks, preflight updated to 8 checks
Phase 5: Vitest + Testing Library + /write-tests skill

- Badge.tsx colour maps unified to CSS variables (D031)
- 5 empty interface→type alias fixes (Switch, Radio, Divider, IconButton, Link)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/skills/audit/SKILL.md

@@ -14,6 +14,7 @@ Run systematic **technical** quality checks on a component or area and generate
 1. Read `docs/design-system.md` for FA design conventions
 2. Read the component/area source files
 3. Reference `docs/reference/impeccable/` for detailed design guidelines when scoring
+4. Reference `docs/reference/vercel/web-design-guidelines.md` for additional WCAG/accessibility rules (optional, for deeper a11y scoring)
 
 ## Diagnostic Scan