VCS UCLI checkpoint/save errors arrive as normal output; check for Error-[

When driving a VCS simulation through UCLI commands from a controller process, refusals such as UCLI-SAVE-STOP (save while stopped at a $stop task) and UCLI-CHECKPOINT-INVALID-ID (restore of a checkpoint id that does not exist) come back as ordinary command output, not as a failure status. A wrapper that only checks that a reply arrived will report success, and an invalid restore can still reset wrapper-side state like watch lists. Scan the reply for the 'Error-[' prefix and turn it into an error. Tests should assert real outcomes (the save file exists, state rewound to the checkpoint value and time), not just an ok reply. A test that only checks for an ok reply passed even though every save had been refused.