The discord CLI's top-level handler prints a native Node error that is not
already a labelled refusal as 'cannot <syscall> <label> (<CODE>)'. The journal
and approvals readers and writers name the file by label at the source, so
conversation, control-board and webui callers get the label too. The session
directory check moves to engine-pi.mjs as sessionContinues(). Exit codes and
refusal codes are unchanged.