clarified proof_result: finish proof formally via head tr, not end_tr;
clarified proof_result: finish proof formally via head tr, not end_tr;

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle