feat: add --parent flag to bd list command (bd-yqhh)

Filters issues by parent issue ID using parent-child dependencies.

Example: bd list --parent=bd-xyz --status=open

Changes:
- Add ParentID field to IssueFilter type
- Add --parent flag to list command
- Forward parent filter through RPC
- Implement filtering in SQLite and memory storage

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

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

internal/storage/sqlite/queries.go

@@ -1623,6 +1623,12 @@ func (s *SQLiteStorage) SearchIssues(ctx context.Context, query string, filter t
 		}
 	}
 
+	// Parent filtering (bd-yqhh): filter children by parent issue
+	if filter.ParentID != nil {
+		whereClauses = append(whereClauses, "id IN (SELECT issue_id FROM dependencies WHERE type = 'parent-child' AND depends_on_id = ?)")
+		args = append(args, *filter.ParentID)
+	}
+
 	whereSQL := ""
 	if len(whereClauses) > 0 {
 		whereSQL = "WHERE " + strings.Join(whereClauses, " AND ")

internal/storage/sqlite/transaction.go

@@ -1098,6 +1098,12 @@ func (t *sqliteTxStorage) SearchIssues(ctx context.Context, query string, filter
 		}
 	}
 
+	// Parent filtering (bd-yqhh): filter children by parent issue
+	if filter.ParentID != nil {
+		whereClauses = append(whereClauses, "id IN (SELECT issue_id FROM dependencies WHERE type = 'parent-child' AND depends_on_id = ?)")
+		args = append(args, *filter.ParentID)
+	}
+
 	whereSQL := ""
 	if len(whereClauses) > 0 {
 		whereSQL = "WHERE " + strings.Join(whereClauses, " AND ")