update /editor to new slash command arch (#4153)

Co-authored-by: Abhi <abhipatel@google.com>

packages/cli/src/ui/commands/editorCommand.ts

@@ -0,0 +1,16 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { type OpenDialogActionReturn, type SlashCommand } from './types.js';
+
+export const editorCommand: SlashCommand = {
+  name: 'editor',
+  description: 'set external editor preference',
+  action: (): OpenDialogActionReturn => ({
+    type: 'dialog',
+    dialog: 'editor',
+  }),
+};