Write Docs

A doc is a glossary: it names the moving parts, says why each exists, and carries the principles a reader can't derive by grepping. The code is the source of truth for what exists right now — the doc must never race it. Before writing any line, ask the one question that governs this skill: could the reader get this faster and more reliably by reading the code? If yes, point them at the code instead of copying it in.

Keep vs shed

Keep — a reader cannot grep their way to these:

• The WHY: why a thing exists, the principle behind a split, the taxonomy file names don't reveal.
• Non-obvious discoveries: platform quirks, "if you remove this, X breaks because Y", a contract two files silently share.
• Pointers to where things live, and what KIND of thing lives there plus the rule for what belongs.