transition to using Three's standard y-up

[ahdinosaur]

allow CAD environment to be z-up, while the Three render is y-up.

https://github.com/sgenoud/replicad handles this somehow. nevermind

so what about a transform?

• Three is right-handed y-up, we want right-handed z-up.
• https://discourse.threejs.org/t/switch-matrix-from-y-up-to-z-up/13331/2

this would enable using more helpers from @react-three/drei, e.g. AccumulativeShadows