script/lint builds Dockerfile.lint only for the exit status, but every
run exported the result as an image: seconds spent exporting, and one
untagged image left behind each time. It now builds with
--output=type=cacheonly, so nothing is exported. CHECK_EPOCH still
changes on every run, so the gate steps still run each time; the build
cache is kept as before.
Model: opus-5-5
sneak