feat: add bd doctor check for orphaned issues (bd-5hrq)

- Add CheckOrphanedIssues to detect issues referenced in commits but still open
- Pattern matches (prefix-xxx) in git log against open issues in database
- Reports warning with issue IDs and commit hashes
- Add 8 comprehensive tests for the new check

Also:
- Add tests for mol spawn --attach functionality (bd-f7p1)
- Document commit message convention in AGENT_INSTRUCTIONS.md
- Fix CheckpointWAL to use wrapDBError for consistency

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

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

cmd/bd/doctor.go

@@ -719,6 +719,11 @@ func runDiagnostics(path string) doctorResult {
 	result.Checks = append(result.Checks, syncBranchHealthCheck)
 	// Don't fail overall check for sync branch health, just warn
 
+	// Check 17b: Orphaned issues - referenced in commits but still open (bd-5hrq)
+	orphanedIssuesCheck := convertWithCategory(doctor.CheckOrphanedIssues(path), doctor.CategoryGit)
+	result.Checks = append(result.Checks, orphanedIssuesCheck)
+	// Don't fail overall check for orphaned issues, just warn
+
 	// Check 18: Deletions manifest (legacy, now replaced by tombstones)
 	deletionsCheck := convertWithCategory(doctor.CheckDeletionsManifest(path), doctor.CategoryMetadata)
 	result.Checks = append(result.Checks, deletionsCheck)