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.test.ts

@@ -0,0 +1,38 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, beforeEach } from 'vitest';
+import { modelCommand } from './modelCommand.js';
+import { type CommandContext } from './types.js';
+import { createMockCommandContext } from '../../test-utils/mockCommandContext.js';
+
+describe('modelCommand', () => {
+  let mockContext: CommandContext;
+
+  beforeEach(() => {
+    mockContext = createMockCommandContext();
+  });
+
+  it('should return a dialog action to open the model dialog', async () => {
+    if (!modelCommand.action) {
+      throw new Error('The model command must have an action.');
+    }
+
+    const result = await modelCommand.action(mockContext, '');
+
+    expect(result).toEqual({
+      type: 'dialog',
+      dialog: 'model',
+    });
+  });
+
+  it('should have the correct name and description', () => {
+    expect(modelCommand.name).toBe('model');
+    expect(modelCommand.description).toBe(
+      'Opens a dialog to configure the model',
+    );
+  });
+});