fix: show expert outputs before synthesis

Parallel expert runs previously exposed only child status, while the synthesized answer appeared above the expert cards. Each expert now retains and exposes its complete output, the cards can be expanded, and the final synthesis is rendered beneath them and persisted with the conversation.

Release note: 多专家并行分析现在可展开查看每位专家的完整输出，并在其下方显示总 Agent 的综合结果。

src/main/assistant/subagent-service.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it, vi } from 'vitest'
 import type { AssistantExpert } from '../../shared/assistant-contracts'
+import type { SubagentEvent } from '../../shared/contracts'
 import type {
   AgentExecutionRequest,
   AgentRuntime
@@ -36,10 +37,15 @@ function database() {
 describe('SubagentService', () => {
   it('creates a linked child task and puts expert instructions in system context', async () => {
     let executionRequest: AgentExecutionRequest | undefined
+    const expertOutput = '结果'.repeat(35_001)
     const runtime = {
       run: async function* (request: AgentExecutionRequest) {
         executionRequest = request
-        yield { requestId: request.requestId, type: 'text', delta: '结果' } as const
+        yield {
+          requestId: request.requestId,
+          type: 'text',
+          delta: expertOutput
+        } as const
         yield { requestId: request.requestId, type: 'done' } as const
       },
       releaseConversation: vi.fn(async () => undefined),
@@ -51,16 +57,17 @@ describe('SubagentService', () => {
       db as never,
       new SubagentScheduler({ timeoutMs: 1_000 })
     )
-    const events: string[] = []
+    const events: SubagentEvent[] = []
     const result = await service.run({
       parentRequest,
       expert,
       routingMode: 'smart',
       signal: new AbortController().signal,
-      onEvent: (event) => events.push(event.state)
+      onEvent: (event) => events.push(event)
     })
 
-    expect(result.output).toBe('结果')
+    expect(result.output).toBe(expertOutput)
+    expect(result.output.length).toBeGreaterThan(60_000)
     expect(db.createTask).toHaveBeenCalledWith(
       expect.objectContaining({
         parentTaskId: parentRequest.requestId,
@@ -73,13 +80,27 @@ describe('SubagentService', () => {
     expect(executionRequest?.trustedInstructions).toContain(
       expert.systemInstructions
     )
-    expect(events).toEqual(['queued', 'running', 'completed'])
+    expect(events.map((event) => event.state)).toEqual([
+      'queued',
+      'running',
+      'completed'
+    ])
+    expect(events.at(-1)).toMatchObject({
+      state: 'completed',
+      output: expertOutput
+    })
     await service.dispose()
   })
 
   it('fails tool-producing experts and records bounded failure state', async () => {
+    const events: SubagentEvent[] = []
     const runtime = {
       run: async function* (request: AgentExecutionRequest) {
+        yield {
+          requestId: request.requestId,
+          type: 'text',
+          delta: '部分结果'
+        } as const
         yield {
           requestId: request.requestId,
           type: 'tool',
@@ -98,13 +119,18 @@ describe('SubagentService', () => {
       expert,
       routingMode: 'manual',
       signal: new AbortController().signal,
-      onEvent: vi.fn()
+      onEvent: (event) => events.push(event)
     })).rejects.toThrow('不允许工具调用')
     expect(db.updateTaskStatus).toHaveBeenLastCalledWith(
       expect.any(String),
       'failed',
       expect.stringContaining('不允许工具调用')
     )
+    expect(events.at(-1)).toMatchObject({
+      state: 'failed',
+      output: '部分结果',
+      error: expect.stringContaining('不允许工具调用')
+    })
     await service.dispose()
   })