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.

Yes, I'm talking about a UX that could handle that for the programmer instead, as an example. Zoom out a bit :)