Hygiene-by-default was already present: user operatives close over
static-env and bind formals + body $define!s in (extend STATIC-ENV),
caller's env untouched. $let evaluates values in caller env, binds
in fresh child env, runs body there. $define-in! explicitly targets
an env. Full scope-set / frame-stamp hygiene is research-grade
and documented as deferred future work in the reflective API notes.
