One connector: the vocabulary it is drawn in, and its SVG path data.
kind is what the stylesheet reads to pick a stroke token, and it is
derived from the slot's style through ViewModel.exit_edge/1 rather
than from any type name (ADR-0005 decision 10h).
There are four kinds and there is deliberately no fifth for a failure
rail. sb-67s ruled that a failure exit leaves by the ORDINARY flow
edge, and the spike's own assertion of that ruling is the sentence
"a failure exit takes no class of its own": it shares one stylesheet
rule with the edge between two adjacent steps, so it can never pick up
the dashes or the warning hue that mark a way out of band. Giving it a
:failure kind here would have re-created the distinction the ruling
removed, one layer down.