snap_resize ran snap_rect on the whole box, which looks at all three
edges on each axis and takes the nearest line. A fixed edge already on a
line (distance 0) always won, so the dragged edge never snapped; a fixed
edge near a line moved the dragged edge by its own distance. Resizing now
looks only at the dragged edges (snap_edges), also for the grid fallback.
Co-Authored-By: Claude <noreply@anthropic.com>