feat(cli): add create command with interactive block selection

- register create command in Commander program
- add @inquirer/prompts dependency for interactive prompts
- extend Block type with optional repo field
- scaffold create command module with initial implementation

package.json

@@ -32,6 +32,7 @@
   },
   "license": "MIT",
   "dependencies": {
+    "@inquirer/prompts": "^8.5.2",
     "commander": "^15.0.0",
     "js-yaml": "^5.0.0"
   }