After the cherry-pick step in run_squash_merge, verify:
1. project_root is on the base branch (not a merge-queue branch)
2. HEAD commit has actual code changes (not an empty/story-only diff)
If either check fails, return success=false so the story stays in merge
stage for retry instead of being phantom-advanced to done.
Also rename move_story_to_archived → move_story_to_done.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
dave