perf: parallelize Storybook tests in CI with 2 workers

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: Simon Bigelmayr

.github/workflows/validate.yml

@@ -67,4 +67,4 @@ jobs:
         run: |
           npx http-server storybook-static --port 6006 --silent &
           npx wait-on tcp:6006
-          yarn run test:storybook
+          yarn run test:storybook --maxWorkers=2