Main points:

- at the moment CI is run on PR and on Merge. Convert to only running on PR commits. I've just submitted a PR to do this for numpy.

- add a manual trigger. Simple to achieve, but requires input from a maintainer.

- reduce wheel build frequency. At the moment I believe they're made every week. However, that decision has to factor in the increased frequency that may be desired as numpy2.0 is worked on.