Add version-file input to the Flux CLI action

[somaz94]

The Flux CLI action can now read the version from a file via a new version-file input, so the version can be pinned in a .tool-versions (asdf) or plain version file instead of hardcoded in the workflow. The input is ignored when version is set, so existing workflows are unaffected.

Validation:

• YAML lint of action/action.yml and the workflow: pass
• Local simulation of the resolution logic (plain file, .tool-versions with flux/flux2 key, v prefix, missing-file and empty-file errors) behaves as expected
• Added a version-file CI job in .github/workflows/action.yaml exercising both fixture formats

AI assistance was used for this change, disclosed via the Assisted-by commit trailer.

[stefanprodan]

Let's make the .tool-versions install 2.9.2 and test here the version

[somaz94]

Done — the .tool-versions fixture now installs flux 2.9.2 (distinct from the plain .flux-version fixture's 2.8.8), and the assert step checks for 2.9.2. The differing versions prove the CLI version is resolved from the .tool-versions file rather than coincidentally matching a shared value. Pushed in ba9a4c6.

[stefanprodan]

Please squash the 2 commits and force push, your last commit has no signoff.

[somaz94]

Squashed into a single signed-off commit and force-pushed — DCO should be green now. Regarding the .tool-versions version: the fixture already installs a distinct flux 2.9.2 (vs 2.8.8 in the plain .flux-version fixture), and the CI job asserts it with flux -v | grep -q '2.9.2', so the resolved version is verified end-to-end. Thanks for the review!

[stefanprodan]

LGTM

Thanks @somaz94