feat(chat): 访客与客服聊天界面、历史拉取与断线重连

聊天页支持发送确认、历史补拉和重连；刷新后不重复展示已确认消息。

frontend/src/__tests__/utils/chatActions.spec.ts

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+/*
+Copyright 2024-2026 ReplyPier
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { routeChatToHuman } from '@/utils/chatActions'
+import { chatService } from '@/services/chat'
+
+vi.mock('@/services/chat', () => ({
+  chatService: { routeToHuman: vi.fn() },
+}))
+
+const toastSuccess = vi.fn()
+const toastError = vi.fn()
+vi.mock('vue-sonner', () => ({
+  toast: {
+    success: (...args: unknown[]) => toastSuccess(...args),
+    error: (...args: unknown[]) => toastError(...args),
+  },
+}))
+
+describe('routeChatToHuman', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('returns the updated chat the endpoint sends back', async () => {
+    const updated = { session_id: 's1', status: 'transferred', user_id: null }
+    vi.mocked(chatService.routeToHuman).mockResolvedValue(updated as never)
+
+    await expect(routeChatToHuman('s1')).resolves.toBe(updated)
+    expect(toastSuccess).toHaveBeenCalled()
+    expect(toastError).not.toHaveBeenCalled()
+  })
+
+  it('surfaces the server reason and returns null on failure', async () => {
+    vi.mocked(chatService.routeToHuman).mockRejectedValue({
+      response: { data: { detail: 'A human is already handling this chat' } },
+    })
+
+    await expect(routeChatToHuman('s1')).resolves.toBeNull()
+    expect(toastError).toHaveBeenCalledWith(
+      '转交会话失败',
+      expect.objectContaining({ description: 'A human is already handling this chat' })
+    )
+  })
+})