NewDummyGui creates a new dummy GUI for testing.

for now the split view will always be on NewGui builds a new gui handler.

using this wrapper for when an onFocus function doesn't care about any potential props that could be passed.

OverlappingEdges determines if panel edges overlap.

Gui wraps the gocui Gui object which handles rendering and events.

this gives our integration test a way of interacting with the gui for sending keypresses and reading state.

we keep track of some stuff from one render to the next to see if certain things have changed.