When selecting a floor slab or ceiling node, the floating UI buttons now
include a cut-out icon (carbon:cut-out) that directly creates a hole and
enters edit mode. Much more intuitive than navigating to the side panel.
Changes:
- NodeActionMenu: add onAddHole prop with carbon:cut-out icon
- FloatingActionMenu: wire up handleAddHole for slab/ceiling types
- Add ceiling to ALLOWED_TYPES so the floating menu appears for ceilings too
- Separate HOLE_TYPES from DELETE_ONLY_TYPES for cleaner type gating
