In a clone where script/bootstrap has not run, node_modules/ is empty and
yarn falls back to whatever prettier is on the PATH, which can format files
differently from the version yarn.lock pins. script/fmt and script/fmt-check
now stop with a message telling the user to run script/bootstrap when
node_modules/.bin/prettier is missing. After bootstrap they behave as
before. The README Entrypoints entries say so.
Model: opus-5-5
sneak