change 'move-mode.sml' to use layer tree everywhere instead of squares

fcore/app-with.sml

@@ -19,62 +19,6 @@ struct
           Vector.tabulate (maxPoints, fn _ => {r = 0, g = 0, b = 0, a = 0}))
     end
 
-  fun squares (app, newSquares) =
-    let
-      val
-        { mode
-        , squares
-        , arrowX
-        , arrowY
-        , canvasWidth
-        , canvasHeight
-        , windowWidth
-        , windowHeight
-        , xClickPoints
-        , yClickPoints
-
-        , showGraph
-        , mouseX
-        , mouseY
-        , openFilePath
-        , fileBrowser
-        , fileBrowserIdx
-        , r
-        , g
-        , b
-        , a
-        , layer
-        , layerTree
-        , modalNum
-        } = app
-    in
-      { mode = mode
-      , squares = newSquares
-      , arrowX = arrowX
-      , arrowY = arrowY
-      , canvasWidth = canvasWidth
-      , canvasHeight = canvasHeight
-      , windowWidth = windowWidth
-      , windowHeight = windowHeight
-      , xClickPoints = xClickPoints
-      , yClickPoints = yClickPoints
-
-      , showGraph = showGraph
-      , mouseX = mouseX
-      , mouseY = mouseY
-      , openFilePath = openFilePath
-      , fileBrowser = fileBrowser
-      , fileBrowserIdx = fileBrowserIdx
-      , r = r
-      , g = g
-      , b = b
-      , a = a
-      , layer = layer
-      , layerTree = layerTree
-      , modalNum = modalNum
-      }
-    end
-
   fun arrowX (app, arrowX) =
     let
       val