fix(done): create MR beads as ephemeral wisps

MR beads were being created as regular beads, showing up in `bd ready`
when they should be ephemeral wisps that get cleaned up after merge.

Added Ephemeral field to CreateOptions and set it when creating MR beads.

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

internal/beads/beads.go

@@ -86,6 +86,7 @@ type CreateOptions struct {
 	Description string
 	Parent      string
 	Actor       string // Who is creating this issue (populates created_by)
+	Ephemeral   bool   // Create as ephemeral (wisp) - not exported to JSONL
 }
 
 // UpdateOptions specifies options for updating an issue.
@@ -391,6 +392,9 @@ func (b *Beads) Create(opts CreateOptions) (*Issue, error) {
 	if opts.Parent != "" {
 		args = append(args, "--parent="+opts.Parent)
 	}
+	if opts.Ephemeral {
+		args = append(args, "--ephemeral")
+	}
 	// Default Actor from BD_ACTOR env var if not specified
 	actor := opts.Actor
 	if actor == "" {

internal/cmd/done.go

@@ -262,6 +262,7 @@ func runDone(cmd *cobra.Command, args []string) error {
 				Type:        "merge-request",
 				Priority:    priority,
 				Description: description,
+				Ephemeral:   true,
 			})
 			if err != nil {
 				return fmt.Errorf("creating merge request bead: %w", err)