feat: add core package

Add @puaros/core package with TypeScript configuration, Vitest test setup, and package structure

packages/core/tsconfig.json

@@ -0,0 +1,20 @@
+{
+  "compilerOptions": {
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "target": "ES2023",
+    "module": "CommonJS",
+    "moduleResolution": "node",
+    "declaration": true,
+    "declarationMap": true,
+    "composite": true,
+    "esModuleInterop": true,
+    "allowSyntheticDefaultImports": true,
+    "strict": true,
+    "skipLibCheck": true,
+    "sourceMap": true,
+    "baseUrl": "./src"
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "dist", "**/*.spec.ts", "**/*.test.ts"]
+}