Replaced the NotImplementedError stub with a full animation
implementation. Entity3D now supports animating: x, y, z,
world_x, world_y, world_z, rotation, rot_y, scale, scale_x,
scale_y, scale_z, sprite_index, visible.
Added Entity3D as a third target type in the Animation system
(alongside UIDrawable and UIEntity), with startEntity3D(),
applyValue(Entity3D*), and proper callback support.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
