Add validate-generated-nix CI job
Summary
Adds a CI job to validate that generated Nix files are up-to-date by running horizon-gen-nix 0.14.0 and checking for any differences.
Changes:
- Add
validate-generated-nixjob innix/ci.nix - Job runs in the
validatestage - Executes
horizon-gen-nix 0.14.0from remote - Fails if
git diffshows any changes
This ensures that the committed generated files match what would be produced by the generator, preventing drift between the generator and committed files.