`_prepend_path` inserted the resolved command's directory only when it was
absent from the child's PATH. The Hermes installer appends its managed Node
dir to the user PATH, so for anyone with a system Node (<22.12) earlier on
PATH the check no-oped and the managed dir stayed behind it. npm lifecycle
children (`node install.js`) then resolved the older system Node and failed
with ERR_REQUIRE_ESM even though Hermes had provisioned a compatible runtime.
Strip every existing case/trailing-separator variant of the directory first,
then prepend it, so the canonical entry is the one that wins and PATH does
not grow duplicates.
Fixes#82309
79dbb1450e