test: move stream harness into vitest

packages/app/vitest.config.ts

@@ -0,0 +1,14 @@
+import { defineConfig } from "vitest/config";
+import path from "path";
+
+export default defineConfig({
+  test: {
+    environment: "node",
+  },
+  resolve: {
+    alias: {
+      "@": path.resolve(__dirname, "src"),
+      "@server": path.resolve(__dirname, "../server/src"),
+    },
+  },
+});