I think the best solution is to use something like webpack or vite or whatever. These usually have their own dev server and can watch directories for changes.

I think the best solution is to use something like webpack or vite or whatever. These usually have their own dev server and can watch directories for changes. My personal site is also using a custom make-like ssg, but after spending a disproportionate amount of time writing the bundling/packaging code, I decided to just switch over to one of these tools. It’s a solved problem, and it greatly reduced the complexity of my site.