v0.2.1 — fresh-install fix

Patch release, found by post-release adversarial review of v0.2.0.

• Fixed (critical for new users): tabula build failed on a fresh npm install — @tailwindcss/postcss was only a devDependency of @tabula-css/registry while the registry generator imports it at runtime (TAB-E902: Cannot find package '@tailwindcss/postcss'). Present since v0.1.0, masked by the monorepo. It is now a real dependency; a fresh npm install + npx tabula build works end-to-end (verified from packed tarballs: build → scan gate → stock-Tailwind compile → cn() → eject).
• Fixed: the ESLint plugin now enforces the variant-product closure. no-unknown-class previously accepted undeclared chains (hover:p-md, md:bg-surface) that emit no CSS — the only one of the four validation surfaces (merge, scan, types, lint) with the gap. It now mirrors the merge gate and reports an accurate TAB-E230 message.
• Docs: getting-started now lists all 12 artifacts (including the canonical tabula.config.json provenance copy), in English, 한국어, 日本語, 简体中文.

All 10 packages published in lockstep at 0.2.1 with npm provenance.