DEVLOG #30 - I can now undo a model update through the full practice loop

SL-LLM-R needs a complete way to undo a model change before real learning updates can be trusted. I can now save the original model, make a changed copy, test it, switch to it, and return to the original in one practice run. I have not yet used that path to undo a genuinely learned LLM update, so the mechanism works but the real learning case is still untested.