I just installed the same version 0.3.4 of the program and it runs fine on both Powershell and Git Bash:
The problem you're having is from Git Bash, not from Celest CLI. You can try these solutions:
According to this, Running Git Bash as administrator once fixes the issue. If this doesn't work, the next one will definitely work.
From this issue in git-for-windows/git repository, uninstalling and reinstalling git solved the issue for some persons. Try to update your Git from time to time.
I went to https://celest.dev/download and used the windows x64 installer.
git bash is a common terminal used for Windows devs. This seems to be an issue from the installer side.
After installing, my environment reproduces the following:
git bash
powershell
Expectation
Windows installer installs the celest exe without issue for git bash.