Refinery as worktree: local MR integration (gt-4u5z)

Architecture changes:
- Refinery created as worktree of mayor clone (shares .git)
- Polecat branches stay local (never pushed to origin)
- MRs stored as wisps in .beads-wisp/mq/ (ephemeral)
- Only main gets pushed to origin after merge

New mrqueue package for wisp-based MR storage.
Updated spawn, done, mq_submit, refinery, molecule templates.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/beads/molecules_patrol.go

@@ -601,7 +601,7 @@ git checkout main
 git merge --ff-only temp
 git push origin main
 git branch -d temp
-git push origin --delete <polecat-branch>
+git branch -D <polecat-branch>  # Local delete (branches never go to origin)
 ` + "```" + `
 
 Main has moved. Any remaining branches need rebasing on new baseline.