By: Tom Sydney Kerckhove <syd@cs-syd.eu>
mutationCheck: drop the inline 'config' attrset, keep only 'configFile' The 'config' attrset was an awkward halfway house: callers built a Nix-shaped value that we then rendered to YAML via builtins.toJSON. With 'configFile', the YAML is the source of truth, hand-maintained in the consuming repo as a sibling file. Move sydtest's own in-repo checks to this style via ./nix/mutation.yaml.