chore: improve NeMo maintenance path

[lphuc2250gma]

Summary:

• Add or tighten focused edge-case tests or type assertions in tests/conftest.py, tests/hydra/my_app.py related to Python typing, tests, CLI ergonomics, observability; avoid docs-only changes and broad refactors.
• Keep the change narrow so it is straightforward to review.

Notes:

• I kept this scoped to the relevant implementation and tests.

[copy-pr-bot]

This pull request requires additional validation before any workflows can run on NVIDIA's runners.

Pull request vetters can view their responsibilities here.

Contributors can view more details about this message here.