I ask juniors to do just as you do. There's a contract specified in the API spec and relevant documents. In kind, I build up an "AI" package one module at a time by specifying contracts for each module. The principle remains the same but at a smaller scale because, as you say, LLMs don't learn.

I know the organizational style doesn't fit a typical "production" set up, but the reality is the code produced is very good. I only set it up this way so I guarantee I can continue iterating on a module without too much pain.

Also, who cares if I have a way more files if I'm still building features for my customers?