fabric-vdr-formal: a Lean 4 model and machine-checked proofs of guarded revocation on a Hyperledger Fabric verifiable data registry

A Lean 4 model of guarded revocation on a Hyperledger Fabric verifiable data registry, with machine-checked proofs that two parties who guard each other's registries do not both commit their revocations. This is the formal artifact of the TDK paper Decentralized verifiable credential revocation with atomic test-and-set for cross-organizational settings (Tibor Sinka, BME, 2026): the model, the proofs, an axiom check and the mutations that show each part of the design is needed.