Add a new command that encapsulates all the work needed to migrate a clone
to use the sync.branch workflow for multi-clone setups like Gas Town:
- Validates current state (not on sync branch, not already configured)
- Creates sync branch if it doesn't exist (from remote or locally)
- Sets up git worktree for the sync branch
- Syncs current beads data to worktree
- Commits initial state to sync branch
- Sets sync.branch configuration
- Pushes sync branch to remote
Usage:
bd migrate-sync beads-sync # Basic migration
bd migrate-sync beads-sync --dry-run # Preview changes
bd migrate-sync beads-sync --force # Reconfigure even if set
