test: combined.ww freshness gate in phase-2 (#110)

test/run

@@ -72,6 +72,25 @@ if [ "${UNIT:-0}" != "1" ]; then
 		name=${t##*/}; name=${name%.c}
 		"$0" --one "$RESULTS/$name" "$t" || true
 	done
+
+	# combined.ww freshness gate (#110): 990/995 above unconditionally
+	# regenerate every tracked combined.ww amalgamation, so a diff vs HEAD
+	# here means an embedded source changed without its derived artifact
+	# being regenerated + committed (the #28 staleness hole the per-file
+	# byte-id gates were blind to). git ls-files keeps new combined.ww
+	# auto-covered (rule-13 SSoT). Lives inside the UNIT guard because
+	# test-unit skips 990/995 and thus the regen.
+	name=combined_ww_fresh
+	if git diff --exit-code -- $(git ls-files '*.combined.ww') > /dev/null 2>&1; then
+		printf 'ok   %s\n' "$name" > "$RESULTS/$name.status"
+	else
+		{
+			printf 'FAIL %s (stale; regen + commit the derived amalgamation)\n' "$name"
+			echo '--- stale combined.ww ---'
+			git diff --name-only -- $(git ls-files '*.combined.ww')
+		} > "$RESULTS/$name.status"
+		: > "$RESULTS/$name.fail"
+	fi
 fi
 
 fail=0