test(phase-06): add @ reference e2e scenarios with explainable skip

frontend/tests/e2e/input-and-compose.spec.ts

@@ -120,4 +120,35 @@ test.describe("聊天工作台 / 输入区与发送", () => {
       page.locator(".is-user").filter({ hasText: "重复提交测试" }),
     ).toHaveCount(1);
   });
+
+  test("DF-INPUT-007 输入@时展示文件候选并可选择为引用 chip", async (
+    { page },
+    testInfo,
+  ) => {
+    skipIfMissingThread(testInfo, THREAD_FOR_WELCOME, "FRONTEND_E2E_THREAD_ID");
+    await openChat(page, reuseThreadChatEntry(THREAD_FOR_WELCOME!));
+
+    const textarea = page.locator("textarea[name='message']");
+    await textarea.click();
+    await textarea.fill("@");
+
+    const dropdown = page.locator("[data-slot='dropdown-menu-content']").first();
+    const items = dropdown.locator("[data-slot='dropdown-menu-item']");
+    const itemCount = await items.count();
+    testInfo.skip(itemCount === 0, "当前线程没有可引用文件候选。");
+
+    await items.first().click();
+    await expect(page.getByLabel("移除引用").first()).toBeVisible();
+  });
+
+  test("DF-INPUT-008 失效引用不会阻断文本发送（可解释 skip）", async (
+    { page },
+    testInfo,
+  ) => {
+    skipIfMissingThread(testInfo, THREAD_FOR_WELCOME, "FRONTEND_E2E_THREAD_ID");
+    await openChat(page, reuseThreadChatEntry(THREAD_FOR_WELCOME!));
+
+    // 该场景依赖特定后端/fixture 能制造 stale 引用；若环境无能力则显式跳过。
+    testInfo.skip(true, "当前 E2E 环境无法稳定注入 stale 引用，使用 hooks 单测覆盖软失败逻辑。");
+  });
 });