test(joinir): Phase 124 return-var normalized smoke (VM)

Phase 124-P4:
- Add fixture: apps/tests/phase124_if_only_return_var_min.hako
  - local x; x = 7; print(x); return x
  - Expected output: 7 (print), RC: 7 (return x)
- Add smoke: tools/smokes/v2/profiles/integration/apps/phase124_if_only_return_var_vm.sh
  - NYASH_JOINIR_DEV=1 HAKO_JOINIR_STRICT=1 for dev-only features
  - Accept exit code 7 (return x where x=7) as valid
- Verify all Phase 121/123/118 smokes still PASS

apps/tests/phase124_if_only_return_var_min.hako

@@ -0,0 +1,11 @@
+// Phase 124: If-only return variable minimal test
+// Expected: 7
+
+static box Main {
+    main() {
+        local x
+        x = 7
+        print(x)
+        return x
+    }
+}