Simplify vitest browser configuration

- Use simpler browser config format as recommended
- Remove instances array wrapper
- Config now uses browser.name directly with chromium

Co-authored-by: dgreif <[email protected]>

Author: Copilot

vitest.config.js

@@ -26,15 +26,9 @@ export default defineConfig({
   test: {
     browser: {
       enabled: true,
+      name: 'chromium',
       provider: 'playwright',
-      instances: [
-        {
-          browser: 'chromium',
-          launch: {
-            headless: true
-          }
-        }
-      ]
+      headless: true
     }
   },
   preview: {