To be honest, I'm not quite sure what the ideal UX looks like yet. The AI assisted autocomplete is too little, but the idea of saying "Build X for purpose Y" is too high-level. Maintaining Markdown documents that the AI implements, also feels too high-level, but letting the human fully drive the implementation probably again too low-level.
I'm guessing the direction I'd prefer, would be tooling built to accept and be driven by humans, but allowed to be extended/corrected by AI, or something like that, maybe.
Maybe a slight contradiction, and very wish-washy/hand-wavey, but I haven't personally quite figured out what I think would be best yet either, what the right level actually is, so probably the best I could say right now :) Sorry!
The Markdown documents can be at any level. Just keep asking the AI to break each individual step in the plan down into substeps, then ask it to implement after you review. It's great for the opposite flow too - reverse engineering from working legacy code into mid-level and high-level designs, then proposing good refactors.