Package modversion holds the library's CUE module version helpers: the
rules for turning a version as a caller or subscription writes it into the
form CUE's module machinery requires.
Bare returns v without the "v" prefix: the spelling a catalog's
metadata.version carries and a platform registry entry stamps. It is the
inverse of Canonical and validates nothing either.
Canonical returns v with the "v" prefix CUE module versions require. A bare
SemVer ("1.0.0") gains it; an already-prefixed or empty version is returned
unchanged. It validates nothing: module.NewVersion remains the validator.