Orbital Presence Group

Keyed list enter/exit with staggered enter delays between children.

Wrap a keyed ForEnumerate of OrbitalPresenceGroupItem children, pass a shared motion preset, and tune stagger (default MotionDuration::Normal) for spacing between items. Each item needs a stable index signal and its own show gate.

Stagger delays accumulate via MotionDuration::stagger_step_delay — index 0 enters immediately, index 1 waits one step, index 2 waits two steps, and so on. Use on_after_leave on each item to remove rows from the DOM after the exit animation finishes.