fix: correct WSL2 OS detection by removing PWD-based Windows override

[JheisonMB]

Summary

Fixes a bug in download_cli.sh where WSL2 was incorrectly detected as Windows when executed from a Windows-mounted directory (e.g., /mnt/c/...).
The script previously used $PWD to decide whether to install the Windows or Linux build of goose. In WSL2, uname -s correctly reports "Linux", but the script was overriding this based on the current working directory path. This caused:

• Download of goose-x86_64-pc-windows-msvc.zip instead of the Linux binary
• Installation of a .exe file into a Linux binary path ($HOME/.local/bin/)
• Attempts to use Windows-specific configuration paths (AppData\Roaming)

Testing

• Verified bash -n download_cli.sh passes syntax check
• Manual review of all OS detection branches:
  • Native Windows (WINDIR, msys, cygwin): still detects as windows
  • WSL (from /mnt/c/... or Linux paths): now correctly detects as linux

Related Issues

Relates to #8672

Screenshots/Demos (for UX changes)

After: