feat: 按机器人选择 Agent Preset

在九个渠道的设置页卡片上选择 Host 已有预设；未选则跟随默认，只影响之后新建的会话。

Co-authored-by: Cursor <cursoragent@cursor.com>

test/channels/whatsapp/client-ui.test.mjs

@@ -69,6 +69,7 @@ test('WhatsApp account card uses the unified compact channel layout', () => {
   assert.match(markup, /WhatsApp Web/);
   assert.match(markup, /检查连接/);
   assert.match(markup, /移除接入/);
+  assert.match(markup, /class="dim-presetSelect"/);
   assert.match(markup, /role="status"[^>]*>测试消息已发送/);
   assert.equal((markup.match(/class="ddt-metric dim-botMetric"/g) ?? []).length, 2);
 });