chore: make CLI executable after build

Adds chmod +x to build script for development use (running CLI
directly without npm install).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: cevian

packages/core/package.json

@@ -22,7 +22,7 @@
     "templates"
   ],
   "scripts": {
-    "build": "tsc --build",
+    "build": "tsc --build && chmod +x dist/cli/index.js",
     "test": "vitest run",
     "test:watch": "vitest"
   },