Add base and loft shelves via partition dimensions using clear height

Set the base shelf from clear height and add a second shelf to divide the loft and fix its height from the top partition dimensions.

1. For the base shelf, set the partition height as clear height, not from the floor: subtract skirting and panel thickness.

   ✓ 已于 2026年10月11日 在产品中核实

2. Add another shelf to divide the loft and fix the loft height from the top partition dimensions.

   ✓ 已于 2026年10月11日 在产品中核实