- Add gt mq command group with reject subcommand
- Add FindMR method to locate MRs by ID or branch
- Add RejectMR method to reject MRs with reason
- Add notifyWorkerRejected for optional mail notification
- Add tests for rejection state transitions
Closes gt-svi.5
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
