Function group_move_blocked 

pub fn group_move_blocked(
    indexed: &IndexedDocument<'_>,
    members: &HashSet<Shape>,
    moved: &[(BlockId, GridRect, GridRect)],
) -> bool

The group rule: only a new overlap rejects, so a selection already sitting on its neighbour (a fresh paste) can still be nudged. Intra-group overlaps are ignored — the group keeps its layout.