Idea: Use modules instead of YAML for evals

### Is your feature request related to a problem? Please describe.

So, I don't really understand why you'd want YAML definitions for this, especially given the awkward assertion code.

### Describe the solution you'd like

It would make more sense to me to use normal Elixir modules with perhaps a helper `use`. Like, why complicate things?

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

Start by reviewing the existing YAML definitions and the assertion code referenced in the issue, then read the comment discussion for the unresolved design concerns. Done means there is an agreed approach for representing evals with Elixir modules and a helper, but the issue does not name files, tests, or more specific acceptance criteria.

Written by the indexing model from the issue text.