Fix NPE and lost chat requests while models are not loaded yet - #503

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: coactions/setup-xvfb@b6b4fcfb9f5a895edadc3bc76318fae0ac17c8b3. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/