Fix: --parent flag now creates parent-child dependency

When using 'bd create --parent <id>', the system now automatically
creates a parent-child dependency linking the child to the parent.
This fixes epic status reporting which was showing zero children.

Fixes #318 (bd-jijf)

Changes:
- cmd/bd/create.go: Add parent-child dependency after issue creation
- internal/rpc/server_issues_epics.go: Add same fix for daemon mode

Tested:
- Created epic with children, verified epic status shows correct count
- Verified closing all children makes epic eligible for closure
- All tests pass

Amp-Thread-ID: https://ampcode.com/threads/T-f1a1aee1-03bd-4e62-a63c-c1d339f8300b
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/create.go

@@ -313,6 +313,18 @@ var createCmd = &cobra.Command{
 			os.Exit(1)
 		}
 
+		// If parent was specified, add parent-child dependency
+		if parentID != "" {
+			dep := &types.Dependency{
+				IssueID:     issue.ID,
+				DependsOnID: parentID,
+				Type:        types.DepParentChild,
+			}
+			if err := store.AddDependency(ctx, dep, actor); err != nil {
+				fmt.Fprintf(os.Stderr, "Warning: failed to add parent-child dependency %s -> %s: %v\n", issue.ID, parentID, err)
+			}
+		}
+
 		// Add labels if specified
 		for _, label := range labels {
 			if err := store.AddLabel(ctx, issue.ID, label, actor); err != nil {