Convert app into @modernsk/ui component library package

- Add library entry (src/index.ts) re-exporting all components, theme,
  and TooltipProvider
- Add shippable stylesheet (src/styles/index.css): tokens + components
  only, font inlined as base64 at build time
- Build with tsup (ESM + CJS + .d.ts) and esbuild for CSS
- package.json: exports map, files, sideEffects, peerDependencies
  (react/react-dom), correct deps (radix-ui), prepare-on-install
- Fix phantom dependency: declare radix-ui, drop unused @radix-ui/themes
- Remove Storybook boilerplate, Tailwind/PostCSS (unused)
- Keep App.tsx + Rsbuild as dev-only playground (not published)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -0,0 +1,56 @@
+{
+  "name": "@modernsk/ui",
+  "version": "0.1.0",
+  "description": "ModernSK — tactile, dark-first React component library built on Radix primitives.",
+  "license": "MIT",
+  "type": "module",
+  "sideEffects": [
+    "**/*.css"
+  ],
+  "main": "./dist/index.cjs",
+  "module": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js",
+      "require": "./dist/index.cjs"
+    },
+    "./styles.css": "./dist/styles.css"
+  },
+  "files": [
+    "dist"
+  ],
+  "scripts": {
+    "build": "tsup && npm run build:css",
+    "build:css": "esbuild src/styles/index.css --bundle --loader:.ttf=dataurl --outfile=dist/styles.css",
+    "dev": "rsbuild dev --open",
+    "preview": "rsbuild preview",
+    "lint": "rslint",
+    "format": "prettier --write .",
+    "prepare": "npm run build"
+  },
+  "peerDependencies": {
+    "react": ">=18",
+    "react-dom": ">=18"
+  },
+  "dependencies": {
+    "@phosphor-icons/react": "^2.1.10",
+    "radix-ui": "^1.4.3"
+  },
+  "devDependencies": {
+    "@rsbuild/core": "^2.0.7",
+    "@rsbuild/plugin-babel": "^1.2.0",
+    "@rsbuild/plugin-react": "^2.0.0",
+    "@rslint/core": "^0.5.1",
+    "@types/react": "^19.2.15",
+    "@types/react-dom": "^19.2.3",
+    "babel-plugin-react-compiler": "^1.0.0",
+    "esbuild": "^0.25.0",
+    "prettier": "^3.8.3",
+    "react": "^19.2.6",
+    "react-dom": "^19.2.6",
+    "tsup": "^8.5.0",
+    "typescript": "^6.0.3"
+  }
+}