test: split vitest into unit and gateway

vitest.gateway.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig, mergeConfig } from "vitest/config";
+import baseConfig from "./vitest.config.ts";
+
+const baseTest = (baseConfig as { test?: { exclude?: string[] } }).test ?? {};
+const exclude = baseTest.exclude ?? [];
+
+export default mergeConfig(
+  baseConfig,
+  defineConfig({
+    test: {
+      include: ["src/gateway/**/*.test.ts", "extensions/**/*.test.ts"],
+      exclude,
+    },
+  }),
+);