Fix failing unit tests in CI

vitest.config.ts

@@ -0,0 +1,11 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    // Only the unit tests that live next to the source are run by Vitest. The
+    // e2e specs (*.spec.ts) are run by their own runner, and the component
+    // browser test is run separately.
+    include: ["src/**/*.test.{ts,tsx}"],
+    exclude: ["**/node_modules/**", "e2e/**", "**/*.browser.test.tsx"],
+  },
+});