chore: Limit tests concurrency (#84)

vite.config.ts

@@ -1,12 +1,20 @@
 // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 import { defineConfig } from 'vitest/config';
+import os from 'node:os';
 
 export default defineConfig({
   test: {
     environment: 'node',
     globalSetup: './test/utils/global-setup.ts',
     testTimeout: 15000,
+    poolOptions: {
+      threads: {
+        minThreads: 1,
+        // leave half of CPU capacity for Chrome browser processes
+        maxThreads: Math.max(Math.floor(os.cpus().length / 2), 1),
+      },
+    },
     coverage: {
       enabled: process.env.CI === 'true',
       provider: 'istanbul',