core::Axis3's wire mirror — core's own type carries no serde derive
(Axis3's doc comment: it's a plain repr(usize) enum for internal
indexing, not wire-facing), so this is decode's own translation, the
same reason TransformSpec/TransformSpec3 mirror GeomTransf/
GeomTransf3 rather than deriving on the core type directly.
core::Axis3's wire mirror — core's own type carries noserdederive (Axis3's doc comment: it's a plainrepr(usize)enum for internal indexing, not wire-facing), so this is decode's own translation, the same reasonTransformSpec/TransformSpec3mirrorGeomTransf/GeomTransf3rather than deriving on thecoretype directly.