refactor: switch to tsdown

package.json

@@ -21,6 +21,7 @@
   "devDependencies": {
     "@babel/plugin-syntax-typescript": "^7.25.9",
     "@eslint/js": "^9.23.0",
+    "@oxc-project/runtime": "^0.66.0",
     "@rollup/plugin-babel": "^6.0.4",
     "@types/babel__core": "^7.20.5",
     "@types/babel__helper-module-imports": "^7.18.3",
@@ -35,7 +36,7 @@
     "jsdom": "^26.0.0",
     "prettier": "3.5.3",
     "tslib": "^2.8.1",
-    "tsup": "^8.4.0",
+    "tsdown": "^0.9.6",
     "typescript": "~5.8.2",
     "typescript-eslint": "^8.29.0",
     "vite": "^6.2.5",