List segments without a table
ReadOnlySegmentList is the studio's own sidebar list, published on its own. Reach for it when a narrow column suits the page better than a grid of columns.
segments is the itinerary's own list, as a read hands it back: useItinerary(itineraryId) from @mountaya/client-react answers it as data.segments, in chain order.
Memoize the store with useState(createUiStore), because a fresh instance every render is a different studio on every pass.