Upgrade to node24 runtime and bump default CLI to v2.12.1

[dangrondahl]

Summary

• Updates the action runtime from node20 to node24 to resolve the Node.js 20 deprecation warning in GitHub Actions
• Bumps the default Kosli CLI version from 2.11.43 to 2.12.1

Test plan

• Verify the action runs without the Node.js 20 deprecation warning
• Verify the correct CLI version is installed by default

[mbevc1]

We should also add latest as a possible version value

[dangrondahl]

We should also add latest as a possible version value

Also, I think I just want to make sure with the tech team that it is ok to bump to latest CLI version.

[tooky]

Not for this PR - but how can this action ALWSYS use latest CLI?

[mbevc1]

Not for this PR - but how can this action ALWSYS use latest CLI?

I've had the same comment ↑ 😄

[gsavage]

I would prefer to split these to changes into separate PRs, if possible.

The Node24 upgrade is needed quite soon - can we split that out into a v3 release, whilst we determine what the Kosli CLI version should be?

[mbevc1]

Are we good to merge?