The _login_nous() call site was pre-filling portal_base_url,
inference_base_url, client_id, and scope with pconfig defaults before
passing them to _nous_device_code_login(). Since pconfig defaults are
always truthy, the env var checks inside the function (HERMES_PORTAL_BASE_URL,
NOUS_PORTAL_BASE_URL, NOUS_INFERENCE_BASE_URL) could never take effect.
Fix: pass None from the call site when no CLI flag is provided, letting
the function's own priority chain handle defaults correctly:
explicit CLI flag > env var > pconfig default.
Addresses the issue reported in PR #5397 by jquesnelle.
0496007ca5