feat: 引擎多出口路由/退回/移交/或签补齐 + 定义 layout 坐标

- 多出口：FlwTask 增 edge_name 列（sql/20260916），FlwTaskRepository.claimAndFinish
  同步落列；FlowTaskService.handle 出度>1 时 edgeName 必填；FlowEngine.continueAdvance
  按 edge name 选路（单出口原路径逐字节兼容，未命中不推进）；FlowAdvanceService/
  FlowNodeAdvanceListener 透传；BranchScope 从 FlowEngine 提取
- DefValidator：多出口出口命名必填且同节点唯一；跨分支连线发布期明确拒绝
- 退回 POST /task/{id}/returnBack：默认退主管线最近已批节点，精确失效当前节点待办，
  split 幂等 upsert 使退回重走并行段不撞 flw_branch uk
- 移交 POST /task/{id}/transfer：TRANSFERRED(5)+新建待办，AssigneeResolver.requireUserName
- 或签 ANY 补齐：首个同意失效同节点兄弟待办
- 已办口径/撤回守卫：status in (1,2,4,5)；新事件 flow.returned/flow.transferred
- FlowDiagramService：EdgeVo.name/NodeVo.state/DiagramVo.layout，办件图状态计算
- 新 IT：多出口×3、ANY 或签、退回重走并行段、退回/移交/撤回

mvn test 84/84 绿

src/main/java/com/yunhai/flowcenter/engine/FlowAdvanceService.java

@@ -2,6 +2,7 @@ package com.yunhai.flowcenter.engine;
 
 import com.yunhai.flowcenter.entity.FlwDef;
 import com.yunhai.flowcenter.entity.FlwInstance;
+import com.yunhai.flowcenter.entity.FlwTask;
 import com.yunhai.flowcenter.enums.FlwEnums;
 import com.yunhai.flowcenter.repository.FlwDefRepository;
 import com.yunhai.flowcenter.repository.FlwInstanceRepository;
@@ -27,9 +28,15 @@ public class FlowAdvanceService {
     private final FlwTaskRepository taskRepository;
     private final FlowEngine flowEngine;
 
-    /** @return 是否实际推进了 */
+    /**
+     * @param nodeId   待放行节点
+     * @param edgeName 多出口节点所选出口（办理事件携带）；可空——兜底从该节点
+     *                 最近一条已同意任务的 edge_name 列重放（推进在 AFTER_COMMIT 新事务重查，
+     *                 事件传参只是快路径，落库的值才是权威）
+     * @return 是否实际推进了
+     */
     @Transactional(propagation = Propagation.REQUIRES_NEW)
-    public boolean tryAdvance(Long instanceId, String nodeId) {
+    public boolean tryAdvance(Long instanceId, String nodeId, String edgeName) {
         FlwInstance instance = instanceRepository.findById(instanceId).orElse(null);
         if (instance == null
                 || instance.getStatus() != FlwEnums.InstanceStatus.APPROVING.getCode()) {
@@ -55,7 +62,17 @@ public class FlowAdvanceService {
                     instanceId, instance.getDefId());
             return false;
         }
-        flowEngine.continueAdvance(instance, def, nodeId);
+        String chosen = edgeName;
+        if (chosen == null) {
+            chosen = taskRepository.findByInstanceIdAndStatus(instanceId,
+                            FlwEnums.TaskStatus.APPROVED.getCode()).stream()
+                    .filter(t -> nodeId.equals(t.getNodeId()) && t.getEdgeName() != null)
+                    .max(java.util.Comparator.comparing(
+                            FlwTask::getHandleTime, java.util.Comparator.nullsFirst(java.util.Comparator.naturalOrder())))
+                    .map(FlwTask::getEdgeName)
+                    .orElse(null);
+        }
+        flowEngine.continueAdvance(instance, def, nodeId, chosen);
         instanceRepository.save(instance);
         return true;
     }