Mismatched CompoundSegment and CompoundStyle in SolidModel

This case is currently not handled correctly -- both `meshsized` and `to_primitives` just zip subsegments with substyles, disregarding grid or tag mismatch. These should use the same resolution mechanisms as `to_polygons` (including the re-slicing in #236). I think the cleanest refactor would define `resolve_compound` in analogy with `resolve_periodic`.

Start with meshsized and to_primitives, then compare their compound handling with to_polygons and the resolve_periodic pattern. Review the re-slicing discussed in #236; the work is done when mismatched grids or tags resolve consistently across these paths instead of being zipped directly.

Written by the indexing model from the issue text.