* move useHotkey for undo/redo into App
* _editorView should be private
* get editorView should be a real get method for consistency
* resolve tsc errors
* fmt
* setView, setState are not exposed
* make undo work without editorview when kcl pane is closed
* lint
* circular deps
* resolve circular deps
* fix undo being 1 step late
* unrelated console.warn removed
* fix undo when code pane is closed during editing
* cleanup
* allow undo to get beyond when code editor has been mounted
* fix up clearHistory
* add test for testing Undo with closed code pane
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