Summary

• handle auth_type: oauth_minimax in agent.auxiliary_client.resolve_provider_client
• reuse resolve_minimax_oauth_runtime_credentials() so auxiliary MiniMax OAuth providers get the right token, base URL, and wrapped Anthropics-compatible client
• add regression tests for both the successful credential path and the missing-credentials warning path

Root cause

agent/auxiliary_client.py never handled oauth_minimax, so every auxiliary MiniMax OAuth config fell through to the generic unhandled auth_type warning even though the runtime credential resolver already existed elsewhere.

Validation

• ./scripts/run_tests.sh tests/agent/test_auxiliary_client.py -q -k 'minimax_oauth or AnthropicOAuthFlag'
• ./scripts/run_tests.sh tests/hermes_cli/test_runtime_provider_resolution.py -q -k minimax_oauth
• git diff --check
• uv sync --frozen --extra all
• uv run --frozen ruff check .
• python scripts/lint_diff.py ...
• env -i ... python -m pytest tests/ --collect-only -q --ignore=tests/integration --ignore=tests/e2e -n auto

Fixes #21521