Correct the bit layout for polygon_indices to use bits 0-15 (16 bits)
for vertex index instead of incorrectly claiming bits 0-14 with bit 15
unused. Add separate texture_indices type since these are simple U32
values, not packed like polygon_indices. Clarify num_texture_indices
should equal num_polygons * 3 when textured.
Add animation.ksy documenting the binary format for LEGO Island's
animation files, including keyframe data, actor references, and
optional camera animation. Includes sample file pns065rd.ani.
