Function cache_dir_for_account 

pub fn cache_dir_for_account(provider: &AuthProvider) -> PathBuf

Return the account-scoped cache directory for one provider.

Layout: $HERMES_HOME/cache/auth-cloudflare/<slug>/ where <slug> is the stable 16-hex FNV-1a account hash (AuthProvider::cache_slug). The token never enters the cache path or any file under it.