Minor release adding print groups.
- Adds PRINT_GROUP / G_PRINT_GROUP and Make(data, print_group = ...) for grouped output of boxes, lids, spacers, standalone dividers, box features, feature groups/copies, and labels.
- Replaces the old MMU-layer print switch.
- Adds a print-group regression fixture showing an intact grouped box and exploded grouped pieces.
- Adds normalized CSG baseline comparison to the pre-commit regression process.