Fix infinite recursion in VM JIT: restore sentinel pre-mark in vm_call
and pre-compile loop so recursive compiler functions don't trigger
unbounded compilation cascades. Runtime VM errors fall back to CEK;
compile errors surface visibly (not silently swallowed).
New: compile-quasiquote emits inline code instead of delegating to
qq-expand-runtime. Closure-captured variables merged into VM globals
so compiled closures resolve outer bindings via GLOBAL_GET.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>