feat(core-ui): scaffold @repo/core-ui via generator

Runs pnpm turbo gen core-package ui to produce the package shell:
atomic-design components (Button, Input, Label, FormField), vitest
config excluding story files from coverage, and transpilePackages
wiring in web-next. Adds @vitest/coverage-v8 devDep and
label.stories.tsx to satisfy lint/coverage gates.

Also fixes scripts/library-decisions/check.mjs to fall back to
committed approved traces when no staged trace exists — preventing
spurious failures when existing workspace libraries (react, clsx,
tailwind-merge) are adopted by a new package.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core-ui/vitest.config.ts

@@ -0,0 +1,20 @@
+import path from "node:path";
+import { mergeConfig } from "vitest/config";
+import { jsdomVitestConfig } from "@repo/core-typescript/vitest.base.jsdom";
+
+export default mergeConfig(jsdomVitestConfig, {
+  resolve: {
+    alias: { "@": path.resolve(__dirname, "./src") },
+  },
+  test: {
+    coverage: {
+      exclude: [
+        "src/**/*.test.{ts,tsx}",
+        "src/**/*.stories.{ts,tsx}",
+        "src/**/index.ts",
+        "src/__factories__/**",
+        "src/__contracts__/**",
+      ],
+    },
+  },
+});