lazy-item-grouping-beats-arrangement-gap

A lazy list's spacedBy arrangement applies between every pair of items and compounds with each item's own edge padding, so blocks that must read as one unit belong in ONE item carrying its own tighter spacing rather than in three items relying on the list's gap. Covers why the visible gap appears in no single constant, why an item boundary is a spacing boundary, and what to do when the group is conditional. Use when…