Add an OP-Stack ProtocolVersion type

Add an OP-Stack ProtocolVersion type: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). We're introducing the concept of a Superchain "Protocol Version" — a Semver-compatible identifier that lets nodes reason about which protocol features they support and signal…