/auth/status now returns per-backend status: Claude warns on <24h expiry,
Gemini warns only when oauth_creds.json is missing or has no refresh_token
(access token rotates automatically so expiry_date is not a useful signal).
Banner shows warnings for both backends when needed, and the hint text
names the specific CLI commands to run.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>