Use a single molecule test job (no matrix) on ubuntu-2204 only. This stops the workflow immediately when the first scenario fails instead of wasting time running 3 parallel runners that all fail for the same reason. Multi-platform will be restored once the base scenarios pass. Generated with [Devin](https://devin.ai) Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>