A knob catalogue entry, with what a UI or a coding agent needs to offer a knob and validate its
values with no map loaded. A catalogue may add fields of its own.
Each kind has one union member. A factor, number or offset knob always carries its range, an
enum or enums knob its options, and a colors knob may carry the names it resolves.
A knob catalogue entry, with what a UI or a coding agent needs to offer a knob and validate its values with no map loaded. A catalogue may add fields of its own.