Previously, node selection made no distinction between a frame node and
other nodes. So a frame node would be selected by their whole rect or
center (depending on box/lasso/circle select). As a consequence of this,
box and lasso could not practically be started inside a frame node (with
the intention to select a subset of contained child nodes) because the
frame would be selected immediately and tweak-transforming started.
Circle selecting would always contain the frame node as well (making
transforming a subset of nodes without also transforming the whole frame
impossible).
Now change selection behavior so that for all selection modes only the
border [the margin area that is automatically added around all nodes] of
a frame node is considered in selection. This makes for a much more
intuitive experience when arranging nodes inside frames.