Lazy Level

The component is self-contained: one file, no dependencies, its own palette in the local --vibeui-cascader-012-* variables. Client-side: the chosen branch and leaf live in useState, while the loading flag is derived by comparing «what is shown» with «what is chosen» — setState is never called in the body of the effect and there is no extra render. The delay emulates a request through setTimeout inside useEffect, and the timer is cleared in the cleanup: without that, fast switching overwrites itself and the list ends up holding a branch nobody is on any more. The skeleton repeats the height of the future row, so the panel does not jump when the data arrives, and the list itself is marked aria-busy — a screen reader announces the loading instead of staying silent. The theme comes from the surrounding color-scheme through light-dark(): the panel has no surface of its own by default, it sits directly on the page background and darkens with it, the skeleton fill included.