Whether the rail breaks between rows or reads as one line.
segmented (default) is v1: one segment per row, separated by the item
gap. continuous stretches each segment across that gap so a band reads
as an unbroken line.
Continuity is built per segment rather than from one line behind the run,
so a rejected stretch stays red and an upcoming tail stays dashed.
It applies within a band; the gap between groups stays open, because a
band is a semantic boundary rather than a rendering accident.