Summary

• Add offline pytest coverage for setup_env.py helper behavior
• Cover architecture alias normalization and model-name resolution
• Cover architecture-specific CLI quantization choices without downloads, builds, or GPU paths

Validation

• python3 -m pytest -q tests/test_setup_env_helpers.py
• python3 -m pytest -q
• python3 -m compileall -q setup_env.py tests/test_setup_env_helpers.py
• git diff --check

Refs Scottcjn/rustchain-bounties#1589