Explain a codebase to a new hire

The prompt

Given this file structure and README, write an onboarding walkthrough that explains the architecture in plain language for a junior engineer.

Expected result

A short onboarding doc that walks the folder structure and explains why it is organized that way, written for someone with no prior context.

Why it works

Feeding in the real file tree and README anchors the explanation to what's actually in the repo instead of a generic architecture lecture.