Serializable AHB rulebook data types shared across the workspace.
These are pure data types — no parsing or evaluation logic. The mapping crate
(mig-bo4e) embeds [AhbWorkflow] in its distribution bundle, and the validation
crate (automapper-validation) interprets it. Keeping the types here lets both
depend on the data without a mapping ↔ validation crate edge. This mirrors how
PidRequirements (the BO4E-side rulebook) already lives in the mapping crate.