One port of one elaborated component that a waveform can be taken of. Carries its own width AND its own labels. The width because of elaboration (see the module note). The labels because deriving them needs the simulation too: an IOLabel's name and width come from which member of a same-named group actually drives the net, which is a fact about the built simulation and does not exist in the renderer when the sidecar is simulating. `PortCompType` rather than the UI's `ComponentGroup`: that type is declared in ModelType, which compiles long after this, and classifying a component is a pure function of its type.