feat: split Ordo designer into library monorepo

Extract ordo-designer-vue package with shadcn UI and context-based state; add playground app, library-api docs, and README.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/playground/package.json

@@ -0,0 +1,30 @@
+{
+  "name": "playground",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "run-p type-check \"build-only {@}\" --",
+    "preview": "vite preview",
+    "build-only": "vite build",
+    "type-check": "vue-tsc --build"
+  },
+  "dependencies": {
+    "ordo-designer-vue": "workspace:*",
+    "vue": "^3.5.40",
+    "vue-router": "^5.2.0"
+  },
+  "devDependencies": {
+    "@types/node": "^24.6.0",
+    "@tsconfig/node24": "^24.0.4",
+    "@tailwindcss/vite": "^4.3.3",
+    "@vitejs/plugin-vue": "^6.0.8",
+    "@vue/tsconfig": "^0.9.1",
+    "npm-run-all2": "^9.0.2",
+    "tailwindcss": "^4.3.3",
+    "typescript": "~6.0.0",
+    "vite": "^8.1.5",
+    "vite-plugin-vue-devtools": "^8.1.5",
+    "vue-tsc": "^3.3.7"
+  }
+}