Error messages are sent to stdout, not to stderr

### Describe the Bug

When installing the NixOS package from nixpkgs-unstable, several commands (for example to create completions) throw errors which are written to the completions file, like

> failed to create /homeless-shelter/.config/pangolin: mkdir /homeless-shelter: permission denied
> failed to create /homeless-shelter/.config/pangolin/logs: mkdir /homeless-shelter: permission denied

A workaround can be to set the HOME environment variable in the Nix file.

But the problem also would not occur if pangolin-cli would not write the errors to stdout but to stderr.

Disclaimer: I'm quite new to NixOS but I checked back this matter with a very experienced colleague of mine. If you have any questions, please let me know.

### Environment

- OS Type & Version: NixOS 25.11
- Pangolin Version: 1.18.4
- Gerbil Version:
- Traefik Version:
- Newt Version:
- Client Version: pangolin-cli 0.8.1

### To Reproduce

- Set HOME environment variable to a directory without write permission for regular users (for example /root)
- Run `pangolin completion fish >output.txt`
- Check written file, error messages should be included.

### Expected Behavior

Error messages should be sent to stderr.