chore: update dependency tsdown to ^0.20.0

Author: renovate[bot]

package.json

@@ -82,7 +82,7 @@
     "npm-package-json-lint": "^9.0.0",
     "npm-run-all2": "^8.0.0",
     "prettier": "3.6.2",
-    "tsdown": "^0.13.3",
+    "tsdown": "^0.20.0",
     "typescript": "^5.9.2",
     "typescript-eslint": "8.47.0",
     "vitest": "^4.0.0"