feat(design-system): token re-import + round-trip guarantee and documented consumers

[PAMulligan]

Summary

Completes the v2.0.0 design system export scope (#82). The
/export-design-system command, its output format (CSS vars + JSON + typed TS +
Tailwind preset), and the export-design-system skill already shipped on main
(criteria #1, #2). This PR fills the two remaining gaps:

• chore: rename project to Aurelius and add community files #3 — a defined consumer, and
• Improve visual diff accuracy in Figma-to-React pipeline #4 — a round-trip guarantee.

Key insight

The exported @scope/design-tokens package ships four token artifacts, but only
tokens.json / tokens.ts are lossless snapshots of the lockfile.
tokens.css and tailwind-preset.ts are derived, one-way views (they drop
nested color scales, typography families, textContent, metadata). So the
round-trip goes through tokens.json, the canonical interchange.

What changed

• Re-importer — scripts/import-design-tokens.js (+ .sh wrapper): the
  inverse of the exporter. Reconstructs design-tokens.lock.json from an export
  root, a package dir, or a raw tokens.json (--from), with
  --out/--verify/--force/--json. --verify is the executable form of the
  round-trip guarantee (exit 0 identical, 1 drifted). Exit codes mirror the
  exporter (0/1/2/3).
• Round-trip test — scripts/__tests__/design-system-roundtrip.test.js:
  tokens → export → reimport → deep-equal lockfile, plus --verify, direct
  tokens.json import, and input-validation exit codes (8 tests).
• Consumer contract — docs/design-system-export/consumers.md: the interchange
  table (lossless vs derived), the round-trip guarantee, and how the named
  consumers ingest the export — Aurelius (self re-import), Flavian
  (WordPress/FSE theme.json mapping table + adapter snippet), Nerva (typed
  tokens in a Hono/Workers backend), plus a Style Dictionary note.
• Wiring — re-import/round-trip section added to the export-design-system
  skill and the /export-design-system command; the new script documented in
  CLAUDE.md; a README Documentation Index entry for the consumer doc.
• Design doc — docs/plans/2026-07-01-design-system-export-consumer-roundtrip-design.md.

Acceptance criteria (#82)

• Slash command /export-design-system under .claude/commands/ (already on main; re-import wiring added)
• Output format documented — CSS variables + JSON + typed TS + Tailwind preset; tokens.json is the lossless interchange (Style Dictionary optional)
• Consumer documented — Flavian (theme.json) and Nerva (typed tokens), with mapping tables + examples
• Round-trip test — tokens → export → reimport produces an identical lockfile

Verification

• pnpm vitest run scripts/__tests__/design-system-roundtrip.test.js → 8 passed
• eslint on the new JS → clean
• prettier --check on all new/changed files → clean
• ./scripts/check-doc-counts.sh → 0 drift
• Pre-commit count guard passed on commit

Built TDD: the round-trip test was written first (RED), then the reimporter made it pass (GREEN).

Closes #82