feat: Implement background shell commands (#14849)

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

@@ -0,0 +1,18 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { CommandKind, type SlashCommand } from './types.js';
+
+export const shellsCommand: SlashCommand = {
+  name: 'shells',
+  altNames: ['bashes'],
+  kind: CommandKind.BUILT_IN,
+  description: 'Toggle background shells view',
+  autoExecute: true,
+  action: async (context) => {
+    context.ui.toggleBackgroundShell();
+  },
+};