feat(agent): 持久化Trace并支持SSE恢复

frontend/src/services/agentService.ts

@@ -1,6 +1,6 @@
 import apiClient from './apiClient'
 import { SseClient } from './sseClient'
-import type { AgentRun, AgentEvent, ApiAgentRun, OperationResponse, PageMeta, ToolDefinition, PermissionRequest } from '@/contracts'
+import type { AgentRun, AgentEvent, AgentTraceResponse, ApiAgentRun, OperationResponse, PageMeta, ToolDefinition, PermissionRequest } from '@/contracts'
 
 function toAgentRun(run: ApiAgentRun): AgentRun {
   // API 的 token_usage 是累计值，UI 模型预留了输入/输出拆分字段。
@@ -54,6 +54,13 @@ export async function cancelAgentRun(runId: string): Promise<OperationResponse>
   return apiClient.post(`/api/agent/runs/${runId}/cancel`)
 }
 
+export async function getAgentTrace(
+  runId: string,
+  params?: { after_sequence?: number; limit?: number },
+): Promise<AgentTraceResponse> {
+  return apiClient.get(`/api/agent/runs/${runId}/trace`, { params })
+}
+
 export async function listTools(): Promise<ToolDefinition[]> {
   const response = await apiClient.get<{ items: ToolDefinition[] }>('/api/tools')
   return response.items
@@ -66,12 +73,14 @@ export function streamAgentEvents(
     onError?: (error: Error) => void
     onDone?: () => void
     onOpen?: () => void
-  }
+  },
+  afterSequence = -1,
 ): SseClient {
   // 将通用 SSE 包装成领域事件，Store 无需了解传输层 envelope。
   const client = new SseClient({
-    url: `/api/agent/runs/${runId}/events`,
+    url: `/api/agent/runs/${runId}/events?after_sequence=${afterSequence}`,
     method: 'GET',
+    lastEventId: afterSequence >= 0 ? String(afterSequence) : undefined,
     onEvent: (eventName, data) => {
       handlers.onEvent?.({
         event: eventName as AgentEvent['event'],