New config `order5_austin`: 200 order-5 implication problems over the 130 equations of the ETP blueprint chapter 'Order 5 Austin laws'. All records have answer=null (no ground truth by construction); every problem survived a 3s Vampire+Mace4 race, finite linear-model search, Mace4 30s, and Vampire CASC 120s undecided. Also updates README (configs list, subset docs, schema notes, usage) and adds the metadata sidecar.
