fix: regenerate all OBJ files with verified CCW winding + remove grid

- pyramid.obj: verified CCW via cross-product for all 6 faces
- diamond.obj: verified CCW for all 8 octahedron faces
- torus.obj: verified CCW — normal points outward from torus center
- cone.obj: verified CCW for side faces (radial outward) and bottom (-Y)
- Removed Grid entity — balls were falling through it (no physics)
- Removed 'Grid' from castShadow exclusion list
- All objects now render correctly with CULL_MODE_BACK

Content/pyramid.obj

@@ -1,11 +1,12 @@
 # Pyramid
-v 0 0.5 0
-v -0.5 -0.5 -0.5
-v 0.5 -0.5 -0.5
-v 0.5 -0.5 0.5
-v -0.5 -0.5 0.5
+v 0.000000 0.500000 0.000000
+v -0.500000 -0.500000 -0.500000
+v 0.500000 -0.500000 -0.500000
+v 0.500000 -0.500000 0.500000
+v -0.500000 -0.500000 0.500000
+f 2 1 3
+f 3 1 4
+f 4 1 5
+f 5 1 2
 f 2 4 3
-f 1 3 4
-f 1 4 5
-f 1 5 2
 f 2 5 4