downloading tar.gz is not in tar.gz format

Hello and thank you for this very practical tool.

I think there is a bug somewhere. After having several tar.gz, I downloaded them via the left panel.

When I wanted to "tar xvzf", I got an error "not in gzip format".

Reproduce the issue by downloading a tar.gz through the left panel, then run tar xvzf on the result and check whether it is a valid gzip archive. Done means the downloaded file can be extracted as a tar.gz; no source file or test is named, so locating the implementation requires tracing the download flow.

Written by the indexing model from the issue text.