watchモードが有効になっていなかったので修正

package.json

@@ -7,7 +7,7 @@
   "scripts": {
     "start": "node --import 'data:text/javascript,import { register } from \"node:module\"; import { pathToFileURL } from \"node:url\"; register(\"./loader.mjs\", pathToFileURL(\"./\"));' built/index.js",
     "build": "swc ./src -s -d ./built",
-    "dev": "tsx src/index.ts --watch",
+    "dev": "tsx watch src/index.ts",
     "lint": "eslint --ext .js,.ts,.tsx \"./src/**/*.{js,ts,tsx}\"",
     "lint:fix": "yarn lint --fix",
     "fmt": "prettier --config ./.prettierrc  --list-different \"src/**/*.{js,json,ts,tsx,css,md}\"",