test(gateway): add multi-instance e2e suite

vitest.e2e.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    include: ["test/**/*.e2e.test.ts"],
+    setupFiles: ["test/setup.ts"],
+    exclude: [
+      "dist/**",
+      "apps/macos/**",
+      "apps/macos/.build/**",
+      "**/vendor/**",
+      "dist/Clawdis.app/**",
+    ],
+  },
+});