Implements the 'bd orphans' command to identify issues referenced in commits
but still open in the database, and refactors to eliminate code duplication.
- Creates cmd/bd/orphans.go with Cobra command structure
- Identifies orphaned issues (referenced in git commits but still open/in_progress)
- Supports multiple output formats (human, JSON, detailed)
- Auto-close with --fix flag
DRY refactoring:
- Extracted FindOrphanedIssues() to cmd/bd/doctor/git.go as shared core logic
- Moved OrphanIssue type to cmd/bd/doctor/types.go
- Refactored CheckOrphanedIssues() to use FindOrphanedIssues()
Cherry-picked from PR #767
Co-authored-by: Amp <amp@ampcode.com>
