TODO

* A Monad type for expression edit makers -- with hidden ReaderT for
  ancestry, and ExpressionEditMaker, and only allow recursing and
  passing prefixed ancestry when recursing

* Key to add redex

* Dapaot:
  * Add anim-id-remappings to sugar changes
  * Multi-ids

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* Add JumpTo which gives a hole-like search -- that can sit in a "tab"
  in place of a DefinitionEdit

* ScrollBar

* From Nimrod: TextView returns all character position rects
  * TextEdit uses the character position rects to locate enter cursor

For correctness:

* Lambda unwrap invalidates params

* Need replace/del to mark entire expression hierarchy now unreachable
  as invalidated for delete/modify conflicts