feat(v3): T27 会话式智能体（多轮上下文/停止/对话式 UI，对齐 dsh 范式）

- ToolLoop 增 history 参数（既往轮次折叠为对话上下文，近 6 轮）
- 会话制：AgentSession/SessionStore 持久化 agent_runs/sessions/{sid}.json，
  /agent/sessions CRUD + /agent 带 session_id（继承会话工作区与执行者配置，busy 并发控制）
- POST /agent/{id}/cancel：取消运行中任务
- AgentView 重构为对话式：会话列表 + 居中消息流（用户蓝气泡/助手白卡）+ 底部 composer
  （工作区/执行者/命令 chips，Enter 发送，运行中红色停止钮），工具过程折叠收纳
- 工具步数统计统一至事件写入层并透出 status.tool_calls
- fix(tests): 会话存储测试隔离，防测试数据泄漏进真实 sessions 目录
- 测试 +4，全量 281 passed

webapp/.mimosa/hook-status/sess_e50d4f25-3ac6-43f2-b2f3-8833b3150465-4843032ba9.json

@@ -1,14 +1,14 @@
 {
   "schemaVersion": "mimosa-hook-status/v1",
-  "recordedAt": "2026-09-01T11:06:34.610Z",
+  "recordedAt": "2026-09-01T14:21:11.564Z",
   "sessionId": "sess_e50d4f25-3ac6-43f2-b2f3-8833b3150465",
   "event": "PostToolUse",
   "toolName": "Edit",
-  "file": "src/style.css",
+  "file": "src/views/AgentView.vue",
   "outcome": "clear",
   "coverage": "complete",
   "findingCount": 0,
-  "durationMs": 3,
+  "durationMs": 7,
   "hostState": "hook_complete",
   "reportHint": ".mimosa/reports/"
 }

webapp/src/api/index.ts

@@ -345,22 +345,90 @@ export interface AgentStatus {
   workspace?: string
   executor_model?: string
   mode?: 'single' | 'dual'
+  tool_calls?: number
 }
 
-/** POST /agent：提交智能体任务（executorPoolId 可选：两级模式的执行者/本地小模型） */
-export async function startAgent(task: string, poolId?: string, workspace?: string, executorPoolId?: string) {
+/** POST /agent：提交智能体任务（sessionId 可选：会话式多轮） */
+export async function startAgent(
+  task: string, poolId?: string, workspace?: string,
+  executorPoolId?: string, sessionId?: string,
+) {
   const { data } = await http.post<{
     request_id: string; status: string; model: string
     workspace?: string; mode?: 'single' | 'dual'; executor_model?: string
+    session_id?: string | null
   }>('/agent', {
     task,
     pool_id: poolId || undefined,
     workspace: workspace || undefined,
     executor_pool_id: executorPoolId || undefined,
+    session_id: sessionId || undefined,
   })
   return data
 }
 
+/** POST /agent/{id}/cancel：停止运行中的智能体任务 */
+export async function cancelAgent(requestId: string) {
+  const { data } = await http.post<{ ok: boolean; detail?: string }>(
+    `/agent/${requestId}/cancel`)
+  return data
+}
+
+// ── 智能体会话（dsh 式多轮） ─────────────────────────────────────────────────
+
+export interface AgentSessionBrief {
+  id: string
+  title: string
+  workspace?: string
+  created_at?: number
+  updated_at?: number
+  busy?: boolean
+  pool_id?: string
+  executor_pool_id?: string
+  turns: number | unknown[]
+}
+
+export interface AgentSessionDetail extends AgentSessionBrief {
+  turns: {
+    request_id: string
+    task: string
+    response: string
+    state: string
+    tool_calls: number
+    tokens: number
+    error?: string | null
+    ts?: number
+  }[]
+}
+
+/** POST /agent/sessions：创建会话 */
+export async function createAgentSession(workspace?: string, executorPoolId?: string, title?: string) {
+  const { data } = await http.post<AgentSessionDetail>('/agent/sessions', {
+    title: title || undefined,
+    workspace: workspace || undefined,
+    executor_pool_id: executorPoolId || undefined,
+  })
+  return data
+}
+
+/** GET /agent/sessions：会话列表 */
+export async function listAgentSessions() {
+  const { data } = await http.get<AgentSessionBrief[]>('/agent/sessions')
+  return data
+}
+
+/** GET /agent/sessions/{sid}：会话详情（含轮次） */
+export async function getAgentSession(sid: string) {
+  const { data } = await http.get<AgentSessionDetail>(`/agent/sessions/${sid}`)
+  return data
+}
+
+/** DELETE /agent/sessions/{sid}：删除会话 */
+export async function deleteAgentSession(sid: string) {
+  const { data } = await http.delete<{ ok: boolean }>(`/agent/sessions/${sid}`)
+  return data
+}
+
 /** GET /agent/{id}/status */
 export async function getAgentStatus(requestId: string) {
   const { data } = await http.get<AgentStatus>(`/agent/${requestId}/status`)