_login_nous() was passing pconfig.portal_base_url (hardcoded production
URL) as a fallback when no --portal-url CLI flag was given. This meant
_nous_device_code_login() received a truthy portal_base_url argument
and never reached the env var fallback chain.
Users setting HERMES_PORTAL_BASE_URL or NOUS_PORTAL_BASE_URL in .env
to point at a staging portal were silently ignored — login always went
to production.
Fix: pass None when no CLI flag is provided, letting the downstream
function properly check env vars before falling back to the default.
Fallback chain is now:
1. --portal-url CLI arg
2. HERMES_PORTAL_BASE_URL env var
3. NOUS_PORTAL_BASE_URL env var
4. DEFAULT_NOUS_PORTAL_URL (production)
Same fix applied to inference_base_url for consistency.
bff47eee48