chore(deps): update dependency tsdown to ^0.15.9

Author: renovate[bot]

package.json

@@ -43,7 +43,7 @@
         "eslint-plugin-prettier": "^5.5.3",
         "globals": "^16.3.0",
         "prettier": "^3.6.2",
-        "tsdown": "^0.12.9",
+        "tsdown": "^0.15.9",
         "typescript": "^5.8.3",
         "typescript-eslint": "^8.37.0"
     },