Flip GLM RH_ZO projection Y for Vulkan NDC so world +Y is screen-up
(models were rendered upside-down). Switch 3D mesh pipelines to Clockwise
front faces to match the flipped winding, and align AO/volumetric NDC
reconstruction plus screenToRay.
Remove the leftover shader ambient floor so Camera3D ambient is honored.
Bake Assimp node transforms in Graphics::newMeshFromAssimp(world) and use
it from ClassicScenes/model3d. Add RenderScenes regression coverage for
orientation, ambient, shadows, gbuffer, and node baking without effect
cross-talk.
Co-authored-by: 西风逍遥游 <sunxfancy@gmail.com>