When running on a branch with no upstream (e.g., gastown polecats), output
different SESSION CLOSE PROTOCOL instructions:
- Use 'bd sync --from-main' instead of 'bd sync'
- Skip git push step (branch is local-only)
- Update Sync & Collaboration section to show --from-main
- Update Completing work workflow accordingly
Detection: git rev-parse --abbrev-ref --symbolic-full-name @{u} returns
error if no upstream configured.
Closes bd-4l5
d453c6e9ea