actions/checkout@v4 is a JS action, and act_runner's host-executor JS
action path hits a known upstream caching bug on this runner (nested
hostexecutor/.cache/act path never gets the downloaded action, causing
MODULE_NOT_FOUND on every run). Introducing a config.yaml to work around
it (workdir_parent) triggers a separate act_runner bug requiring a Docker
socket that doesn't exist on this Mac. Side-stepping both by doing the
checkout as a plain shell git clone, which the host executor runs fine.
d9c2035807