Enforce restrictions on a mounted editor. Listeners are registered in the
capture phase on the editing surface so they run before the view's own
clipboard handlers and before anything the host attached; a blocked event
is cancelled and stopped immediately. Returns a disposer that undoes every
change. A headless editor has no surface to guard, so only the flags apply.
Enforce restrictions on a mounted editor. Listeners are registered in the capture phase on the editing surface so they run before the view's own clipboard handlers and before anything the host attached; a blocked event is cancelled and stopped immediately. Returns a disposer that undoes every change. A headless editor has no surface to guard, so only the flags apply.