Resolve only hits from the latest layout, with independent member details.
Optional: topmost hit under (x,y) in media px (relative to the pane plot).
Ungrouped events and group IDs not yet configured remain visible.
Replace data atomically. Caller mutations never change installed events.
Replace the hierarchy; duplicate IDs, missing parents and cycles are rejected.
Layer order vs series: 'bottom' (behind), 'normal' (over), 'top' (overlay).
Resolve only hits from the latest layout, with independent member details.