Elmoed event clean-up

For editors and sub-editors, A HUGE issue is lingering events. They need to be fully cleaned up, and all event hooks need to go tghrough editor graph so that THERE IS NO WAY there is lingering referneces to destroyed editors.

This is causing all sorts of mysterious issues no doubt, e.g. whenever an editor is destroyed, then re-created, in the same slide, mysterious bugginess occurs

All events registerd with .on(...) need to be recorded in the EditorGraph, then with destroy editor all unhooked

Start by locating the EditorGraph and the editor destruction path, then trace event hooks registered through .on(...). Ensure registered hooks are tracked through the editor graph and removed when an editor is destroyed; done means destroyed editors leave no lingering event references.

Written by the indexing model from the issue text.