* fix(quota): restore Grok Settings usage for current CLI auth/billing
Grok CLI no longer stores a top-level access_token or usage.creditUsage.
Read nested auth key tokens and config.used.val so Settings → Usage
shows monthly credits again. Keep legacy shapes and env tokens working.
Fixes#2352
* fix(quota): make Grok auth-file tests work on Windows
Inject homeDir into GrokQuotaProvider like Kimi so nested
~/.grok/auth.json tests do not depend on os.homedir() which
ignores $HOME on Windows (USERPROFILE).