Better Shulker Boxes (BSB)

### Fixed

- **A carried Shulker Box would not go back down.** On 26.3, left-clicking an empty slot with a
  box on the cursor took the box's first stack out instead of placing the box. The click reached
  Minecraft with 26.3's new number for the left button, which it read as a right-click. It now
  goes through Minecraft's own conversion first, so left places and right extracts, as before.

A client game test now picks up a filled box, puts it down in an empty slot, and checks on the
server that the box arrived with everything still inside.