For agents, on top of README.md, which they read first.

• Nothing here is edited to taste. A change to vendored source is a carried patch: its own commit, named for what it does, so it can be found and re-applied after an upstream pull.
• Never write a README.md or CLAUDE.md inside a vendored tree (c/zbanks-alttp/, rust/jgenesis/, rust/jevcrates/). A refresh replaces the directory wholesale and takes ours with it; the chapters that describe them live one level up.