<.summary>

Stands in for a `ConnieUI.Contents.summary/1` while its values are fetched. Container, row and total geometry come from `ConnieUI.Contents.summary_class/1`, the same source the summary itself reads, so the two cannot drift apart into different sizes. `rows` is how many labelled values to reserve. Reserving one too many settles upward into whitespace when the real summary arrives, which is far less jarring than reserving too few and growing downward, so round up when the count is not known ahead of time.