fix: make token cache tests compatible with macOS
Description
- fix: make token cache tests compatible with macOS
The token cache tests were failing on macOS because the test helper function setUserCacheDir() was only setting XDG_CACHE_HOME, which works on Linux but is ignored by Go's os.UserCacheDir() on macOS.
On macOS, os.UserCacheDir() returns $HOME/Library/Caches and does not respect XDG_CACHE_HOME. This caused the test helper writeFSToken() to write tokens to a different location than where the production code was looking for them.
Related Issues
Resolves #[issue_number]