fix: QueryHook does not check that top-level load attributes belong to the hooked model #388

Found while reviewing #386.

QueryHook checks that nested load attributes belong to their parent relationship's model (#382), but top-level attributes cannot be checked at construction: the hook's model is only a generic parameter. A hook on Color with load=[User.group] builds, then fails at query time when group is looked up on the Color alias. A foreign column whose key also exists on the hook's model silently loads that model's column instead.

Expected

Top-level load attributes are checked against the model once the hook is bound to its field or type (the model is known there), raising QueryHookError with the same message style as nested attributes.