Loop closer documenting what 18 feature commits produced. Kernel-on-SX
is 1,398 LoC substrate + 1,747 LoC tests = 3,145 LoC total. Zero
substrate fixes required across the loop. R-1RK core + extras
implemented. Six proposed lib/guest/reflective/ files awaiting second
consumer. Substrate verdict: env-as-value generalises to
evaluator-as-value; the m-eval demo proves it.