I think it belongs to type, but since they use “auto” it looks standalone and can be confused with the “&” operator. I personally always used * and & as a prefix of the variable name, not as a suffix in the type name, except when used to specify types in templates.
IMO it's a separate category of modifiers/decorators to the type, like how adjectives and nouns are distinguished, and the only reason we have the false-choice in C/C++ is because it's not alphanumeric (if the token were e.g. "ref" it would interfere with the type or variable name in either other convention).
If I were forced at gunpoint to choose one of the type or name, "obviously" I would also choose type.