find-cache-dir: please don't use node_modules for this

npm will casually stomp all over node_modules. It’s safest to treat that as its sovereign turf, and never do anything in that folder that isn’t specifically and officially related to the management of packages.

I recommend literally any other folder name. Maybe .coverage_output/ or something? I don’t know. But please not node_modules. You wouldn’t put this stuff in the .git folder, it should be treated with a similar level of concern.