The host runner's Docker CLI forces the buildx path when DOCKER_BUILDKIT=1
is set, but buildx isn't installed on the runner, so the build errored
before starting. Revert the env var and remove the two RUN --mount=type=cache
directives so the legacy builder can parse the Dockerfile. Normal layer
caching still applies; only the npm download cache reuse is lost.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Jason Stedwell
jason