onHover
Observes distinct pointer enter and exit transitions for this modifier's laid-out bounds.
Hover observation never consumes the corresponding move event. It is event-driven: layout movement under a stationary pointer does not create a transition until another move arrives. An owning session detachment emits PointerHoverEvent.Exit for an entered node before retaining the tree for possible reattachment.
Return
this chain with one appended active hover observer.
Parameters
callback
callback receiving distinct typed transitions on the owning tree thread.