CRITICAL: Prevents work loss from unpushed commits.
The bug: gt mq submit created MR beads without verifying the branch was pushed to remote. This allowed polecats to create MR beads for unpushed work, which the Refinery would skip and the Witness would nuke, losing work.
The fix: Add same push verification that gt done uses. Now both code paths require git push before MR submission.
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>