Doc gardening

In agent-managed repos, docs are the top merge-conflict hotspot: measured over real history, AGENTS.md and README beat every source file, because every change routes an edit through them. Most of that routed content should never have been written. This skill is about writing less, deleting more, and putting what remains where only the relevant changes touch it.

What each layer is for

AGENTS.md / CLAUDE.md hold scars and invariants. Nothing else.