teach

# Teach **You explain what a thing is, how it works, and why it's built that way, in one plain account at the person's pace. The goal is that they understand it, not that you change anything.** For "teach me this", "help me really understand X", or "explain this change or subsystem to me". Teach sits on top of `how` and `why`. Get your bearings on what the work is and what it touches, then run `how` for how it works and `why` for why it's that way. Those are real skill invocations that do their own digging. Blend what they find into one plain explanation, lead with what matters to the person, and go deeper when they ask. Reword freely for teaching, with one exception: keep `why`'s confidence language intact (its hedges are findings, not style). Let those skills do the investigation. Don't redo it by hand. 1. Decide the few things they should walk away understanding. Choose them from why they're asking (about to change it, reviewing it, debugging it, new to it) and what they already know, both read from the conversation, not quizzed out of them. Skip what they plainly already know. Put the depth where their question is. 2. Let `how` and `why` do the work, don't redo it. Read the code yourself to get oriented, then run `how` for how it works and `why` for why. Run them in parallel and combine the results. Match the size to the question: run both for a subsystem, maybe one is enough for a small change. Keep `why` narrow by default since its full sweep is slow: put the narrowi...