refactor(test): extract shared gateway hook and vitest scoped config helpers

vitest.scoped-config.ts

@@ -0,0 +1,17 @@
+import { defineConfig } from "vitest/config";
+import baseConfig from "./vitest.config.ts";
+
+export function createScopedVitestConfig(include: string[]) {
+  const base = baseConfig as unknown as Record<string, unknown>;
+  const baseTest = (baseConfig as { test?: { exclude?: string[] } }).test ?? {};
+  const exclude = baseTest.exclude ?? [];
+
+  return defineConfig({
+    ...base,
+    test: {
+      ...baseTest,
+      include,
+      exclude,
+    },
+  });
+}