After Y-snapping, spouses without shared children can land on top of
each other. Detect these overlaps and move the spouse to the nearest
edge of the generation row without affecting other cards.
Remove post-processing collision resolution that fought ELK's layout.
Keep only Y-snapping (same generation = same row) and grid-aligned
connector Y positions. Add offset drop lines for parents with multiple
spouses so each family unit is visually distinct.
Show small child-box indicators at bottom-right of person cards when
descendants exist beyond the current view. Fix both ancestor and
descendant indicators to draw connecting lines behind boxes.
