Persists characteristic declarations and bakes characteristics/0.

The characteristics do DSL section can hold multiple entity kinds — the regular %Characteristic{} declarations (characteristic :name, Module), and the inherited variants (%InheritedCharacteristicDeclaration{} / %ReverseInheritedCharacteristicDeclaration{}) which produce calculations rather than typed characteristic resources.

characteristics/0 bakes only the regular %Characteristic{} declarations, because consumers of the function (the :build action's typed-characteristic creation, the runtime characteristic lookup, etc.) expect every entry to carry :name and :value_type. The inherited variants are kept in DSL state for TransformInheritedRefs to read and become calculations; they don't surface through characteristics/0.