Tokens

Encodes the small integer tokens that ClassRegistry hands to Godot as opaque CVoidPtrs (class_userdata, instance pointer) and back.

We deliberately stuff an integer id into the pointer slot rather than a real Scala-object address: the Scala objects are kept alive by the registry, and the GC never has to chase a fabricated pointer. Conversion is via the Scala Native intrinsics for raw-pointer/word casts.