test(fixtures): add vite-kitchen fixture repo

Minimal Vite + React + TS + Tailwind app with a typed-props Button
component (the future react-docgen-typescript scan target), landed at
fixtures/ outside the pnpm workspace and turbo graph. Its dependencies
exist on paper only — the runner installs them after cloning (story 04);
no lockfile, never pnpm-installed here.

Ignore surfaces follow the docs/product/reference precedent: fallow,
root ESLint, prettier, and the coverage:diff ALLOWED_GLOBS all skip
fixtures/**.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016j8z4VHjedXDTjEDNg7qHK

scripts/coverage/diff.mjs

@@ -55,6 +55,10 @@ const ALLOWED_GLOBS = [
   // Design reference material (ADR-029) — read-only prototypes committed
   // under docs/product/reference/; never executed, never tested.
   /^docs\/product\/reference\//,
+  // Test fixture repos — standalone apps outside the pnpm workspace and
+  // turbo graph (walking-skeleton story 01); served to tests as git remotes,
+  // never executed by vitest, never in any lcov.
+  /^fixtures\//,
   // Shell scripts (not Vitest-covered)
   /\.sh$/,
   /\.bash$/,