feat(cli): Add /model command for interactive model selection (#8940)

Co-authored-by: Miguel Solorio <miguel.solorio07@gmail.com>

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

@@ -0,0 +1,17 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { CommandKind, type SlashCommand } from './types.js';
+
+export const modelCommand: SlashCommand = {
+  name: 'model',
+  description: 'Opens a dialog to configure the model',
+  kind: CommandKind.BUILT_IN,
+  action: async () => ({
+    type: 'dialog',
+    dialog: 'model',
+  }),
+};