Vow::Procedure

A single dispatchable unit: a name plus a callback that takes the call's named args (a Hash of arg name => raw JSON::Any) and the optional per-call Context, and returns a JSON::Any result.

The callback is what the Vow::Exportable macro generates per exported method — it owns required-arg checking, per-arg typed decoding (by name, honoring defaults), the real method call, and result encoding. Methods that don't opt into context simply ignore the second argument. Keeping Procedure this thin (just name + proc) is deliberate: all the static metadata a code generator wants (arg names, types, return type) lives in the separate Manifest layer, so codegen never has to instantiate a service.