@Ann(attr="hardcoded")
class C {}

=>

@Ann(attr=CONST)
class C {
  private static final String CONST = "hardcoded";
}

does not compile.

First, CONST must have package-private access; you can select this yourself in the wizard before the refactoring is performed, but it ought to just not offer private access as an option in this case.

Second, the value needs to be qualified since it is not inside the class body:

@Ann(attr=C.CONST)
class C {
  static final String CONST = "hardcoded";
}