SCI conformance gate (pure Chez)

Re-port the SCI compatibility stress test to joltc: host/chez/run-sci.ss loads
borkdude/sci's own source (vendor/sci, re-vendored) through the spine and
requires its forms to compile+eval. Floor-gated at 160/218 forms (the tail is
genuine host gaps — set! on vars, some macro/def shapes); raise as they close.
Wired into 'make test' (skips if the submodule isn't checked out).

jolt-cf1q.6

Makefile

@@ -4,10 +4,10 @@
 # build step. `make test` is the full gate. `make remint` rebuilds the seed after a
 # source change.
 
-.PHONY: test values corpus unit smoke selfhost certify remint
+.PHONY: test values corpus unit smoke selfhost sci certify remint
 
 # Full gate. Each step exits non-zero on failure, failing the target.
-test: selfhost values corpus unit smoke certify
+test: selfhost values corpus unit smoke sci certify
 	@echo "OK: all gates passed"
 
 # Self-host fixpoint: bootstrap.ss rebuild == checked-in seed.
@@ -30,6 +30,10 @@ unit:
 smoke:
 	@sh host/chez/smoke.sh
 
+# SCI conformance: load borkdude/sci's source through joltc (floor-gated).
+sci:
+	@chez --script host/chez/run-sci.ss
+
 # JVM oracle: certify the corpus against reference Clojure. Skips if clojure absent.
 certify:
 	@if command -v clojure >/dev/null 2>&1; then \