update_stage rebuilt the home from HERMES_HOME with a literal ~/.hermes
fallback while update_lock resolves the same marker through
get_process_hermes_home(). Where the platform default differs (sudo invoker,
data-dir suffix) the two disagreed and the old-shim UI fallback found no
marker, leaving the hand-off window frozen. hermes_constants is stdlib-only,
so the lazy import keeps this module usable under -I -S -B.
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