test: expand formula test beyond basic --version check

[ulises-jeremias]

Context

Formula CI/test currently leans on --version. Expand to a dry-run help invocation and/or offline smoke that does not need network if possible.

Acceptance criteria

• Formula test exercises --help (or equivalent)
• Document any network requirements

[ulises-jeremias]

Taking this one myself — Homebrew/AUR packaging work needs org-specific permissions (tap publish, AUR credentials, distribution secrets), so it is not a good fit for external contributors right now.

If you want to help with related docs/tests that do not require those secrets, ping me in Discord and we can carve out a safe slice.