Gitea Actions does not honor fail-fast/max-parallel for cancelling
other matrix runners when one fails. Use a single molecule job that
runs all (scenario, platform) pairs via run_molecule_parallel.py.
This gives true parallel execution + immediate termination on the
first failure, which is what we need to debug efficiently.
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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
