gufe now requires openff-nagl so it is no longer optional

[lohedges]

A new release of gufe (1.13.0, published 23 September 2026), which we get indirectly through lomap2, now requires the full OpenFF Interchange package. That package brings in the rest of the OpenFF stack, including NAGL and PyTorch. Until now NAGL was an optional dependency, but we would always use it for OpenFF parameterisation when present, unless explicitly disabled. With this change it will be installed wherever lomap2 is, so the default charge model will no longer be AM1-BCC. As a result, some of our tests may fail because they expect charges from the previous model. We may need to decide explicitly whether NAGL is used, rather than relying on whether it happens to be installed.

[lohedges]

Solutions would be:

1. Update any OpenFF parametrisation calls to use use_nagl=False.
2. Update the appropriate reference files and assertions to use the NAGL parameter values.

I think that option 1) is likely the easiest and most reliable route, since 2) relies on the assumption that the NAGL values are unchanged over time. I've never been sure of how NAGL is versioned, particularly for pre 2.3 Sage, where it wasn't part of the force field itself.