Function classifyInsertCut

classifyInsertCut(
    cut: RangeCoords,
    insert: RangeCoords,
    axis: RangeAxis,
): CoordUtils.InsertCutShift
Which of the four InsertCutShift outcomes inserting insert while cutting cut produces.

The gap closes only when the two share a band across axis - the cut then shifts as a whole, and a whole shift is the only kind a rectangle can express. Off that band the source is simply blanked unless the insert would drag part of the cut along with it, which is refused. Excel draws the same four lines.
Parameters
- cut: RangeCoords
  The range being cut.
- insert: RangeCoords
  Where the block lands, sized as dropped - its LEADING edge on axis is the line.
- axis: RangeAxis
  Which way the existing cells shift: Row down, Column right.
Returns CoordUtils.InsertCutShift