in CI, regen all mechanisms and check if there are diffs

[baperry2]

This is to ensure that the committed mechanisms are always consistent with CEPTR. Sometimes people (e.g., me) will update CEPTR and not regenerate all the mechanisms, and the mechanisms that didn't get updated become non-functional.

[Copilot]

Pull request overview

Updates the CEPTR CI job to regenerate all committed chemical mechanisms during CI and fail the build if regeneration changes any tracked files, preventing stale/non-functional committed mechanisms after CEPTR updates.

Changes:

• Replace per-mechanism conversion steps with list-driven conversion for all “regular” mechanisms.
• Add QSS regeneration (qssa + convert) from a QSS mechanism list.
• Add git diff --exit-code checks to fail CI when regeneration modifies tracked files.

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[baperry2]

This might not be viable due to sensitivities in how CEPTR generation that can lead to tirvial differences when mechanisms are regenerated. Going to leave this as a draft.

[baperry2]

@copilot: it seems like the machine generated code from CEPTR can have small variations sometimes, perhaps due to the system it is being run on or differences in dependency versions. Can you suggest what needs to be done within PelePhysics to make the output fully consistent, such that any diffs indicate actual changes?