> I wanted to see if, with the assistance of modern AI, I could reproduce this work in a more concise way, from scratch, in a weekend.

I don't think it counts as recreating a project "from scratch" if the model that you're using was trained against it. Claude Opus 4.5 is aware of the stable-diffusion.cpp project and can answer some questions about it and its code-base (with mixed accuracy) with web search turned off.