Add close reason display for closed issues

- Add CloseReason field to Issue struct
- Add GetCloseReason and GetCloseReasonsForIssues queries
- Batch-load close reasons in scanIssues for efficiency
- Display close reason in bd show output

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

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

internal/storage/sqlite/dependencies.go

@@ -736,6 +736,19 @@ func (s *SQLiteStorage) scanIssues(ctx context.Context, rows *sql.Rows) ([]*type
 		}
 	}
 
+	// Third pass: batch-load close reasons for closed issues
+	closeReasonsMap, err := s.GetCloseReasonsForIssues(ctx, issueIDs)
+	if err != nil {
+		return nil, fmt.Errorf("failed to batch get close reasons: %w", err)
+	}
+
+	// Assign close reasons to issues
+	for _, issue := range issues {
+		if reason, ok := closeReasonsMap[issue.ID]; ok {
+			issue.CloseReason = reason
+		}
+	}
+
 	return issues, nil
 }