fix: 合并 Query Agent 的连续 system messages

tests/unit/query-agent-history.test.ts

@@ -1,5 +1,8 @@
 import { describe, expect, it, vi } from 'vitest'
-import { QueryAgentService, type QueryAgentProvider } from '../../src/main/services/query-agent-service'
+import {
+  QueryAgentService,
+  type QueryAgentProvider
+} from '../../src/main/services/query-agent-service'
 
 function capturingProvider(configured = true): {
   provider: QueryAgentProvider
@@ -54,6 +57,25 @@ describe('QueryAgentService — 历史上下文不改变毕业语义', () => {
     ])
   })
 
+  it('传 conversationScope 时把范围说明合并进唯一的 system message', async () => {
+    const { provider, calls } = capturingProvider()
+    const service = new QueryAgentService(provider, vi.fn())
+
+    await service.run('这个群最近聊了什么', {
+      conversationScope: {
+        scope: { kind: 'current', conversationId: 'fixture-conversation' },
+        label: '当前会话：fixture-group'
+      }
+    })
+
+    expect(calls[0].messages.map((message) => message.role)).toEqual(['system', 'user'])
+    expect(calls[0].messages.filter((message) => message.role === 'system')).toHaveLength(1)
+    expect(calls[0].messages[0]).toMatchObject({
+      content: expect.stringContaining('当前搜索范围（由应用界面决定）：当前会话：fixture-group。')
+    })
+    expect(String(calls[0].messages[0].content)).toContain('你是 TraceMemo 的本地聊天查询助手')
+  })
+
   it('失败分类是 additive 字段：成功时不存在', async () => {
     const { provider } = capturingProvider()
     const service = new QueryAgentService(provider, vi.fn())