Collab undo history and lists

There seems to be a problem with undo history and lists. To reproduce:

- With collab mode enabled (you don't need a peer), create a list
- On the last line press enter to escape out of the list
- Type some characters slowly so they each get an undo history event
- Undo each character and undo back into the list. When you transition from the paragraph to the list the selection point disappears and you have lost your redo history

I'll note that sometimes, depending on a situation I don't understand, I am able to briefly get undo or redo to work. However, it then goes into another situation I don't understand and stops working.

No files, tests, or entry points are named. First reproduce the issue with collab mode enabled by creating and exiting a list, typing characters slowly, and undoing back into the list; done means the selection point remains available and redo history is preserved through that transition.

Written by the indexing model from the issue text.