And to answer the grand-parent:
building infrastructure that will help other parts of the project -- part of why I call myself a ‘middle-end programmer’.
It seems that the author is using "middle-end" in a manner analagous to the more common "front-end" and "back-end".
Exactly what this involves is not entirely clear, but building frameworks, perhaps.
Brooks called that role the toolsmith.
No, it's definitely not.