I cloned the project and running the playground locally. The UI works fine, except I'm not sure how I'm supposed to add datasets when running locally. - I tried "Upload Local Dataset", but when I select a json file from my machine I get the following error: <img width="482" alt="Image" src="https://github.com/user-attachments/assets/20fc36df-95ba-4e59-8fcd-fc17e6256bd7" /> - I also tried "Upload Files or Folder" -> "Local Server", but json files can't be selected in this mode.