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/rpc/protocol.go

@@ -162,6 +162,9 @@ type ListArgs struct {
 
 	// Template filtering (beads-1ra)
 	IncludeTemplates bool `json:"include_templates,omitempty"`
+
+	// Parent filtering (bd-yqhh)
+	ParentID string `json:"parent_id,omitempty"`
 }
 
 // CountArgs represents arguments for the count operation

internal/rpc/server_issues_epics.go

@@ -751,6 +751,11 @@ func (s *Server) handleList(req *Request) Response {
 		filter.IsTemplate = &isTemplate
 	}
 
+	// Parent filtering (bd-yqhh)
+	if listArgs.ParentID != "" {
+		filter.ParentID = &listArgs.ParentID
+	}
+
 	// Guard against excessive ID lists to avoid SQLite parameter limits
 	const maxIDs = 1000
 	if len(filter.IDs) > maxIDs {

internal/storage/memory/memory.go

@@ -571,6 +571,20 @@ func (m *MemoryStorage) SearchIssues(ctx context.Context, query string, filter t
 			}
 		}
 
+		// Parent filtering (bd-yqhh): filter children by parent issue
+		if filter.ParentID != nil {
+			isChild := false
+			for _, dep := range m.dependencies[issue.ID] {
+				if dep.Type == types.DepParentChild && dep.DependsOnID == *filter.ParentID {
+					isChild = true
+					break
+				}
+			}
+			if !isChild {
+				continue
+			}
+		}
+
 		// Copy issue and attach metadata
 		issueCopy := *issue
 		if deps, ok := m.dependencies[issue.ID]; ok {

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 ")

internal/types/types.go

@@ -562,6 +562,9 @@ type IssueFilter struct {
 
 	// Template filtering (beads-1ra)
 	IsTemplate *bool // Filter by template flag (nil = any, true = only templates, false = exclude templates)
+
+	// Parent filtering (bd-yqhh): filter children by parent issue ID
+	ParentID *string // Filter by parent issue (via parent-child dependency)
 }
 
 // SortPolicy determines how ready work is ordered