fix(lastleg): restore fulfillment safeguards and reconcile return regressions

lastleg-service/src/main/resources/openapi/overseas-pda-operations-v1.yaml

@@ -74,19 +74,20 @@ paths:
         '404': { description: 当前绑定仓无此任务 }
   /api/pda/v1/last-leg/outbound-tasks/{taskNo}/pick:
     post:
-      summary: 扫码拣取一件代发箱件
+      summary: 按当前出库任务扫码拣货
+      description: 退货散箱按指定箱唛或SKU提交；选择整托出库的退货任务必须扫描托盘码，不允许逐箱提交。
       parameters: [{ name: taskNo, in: path, required: true, schema: { type: string } }]
       requestBody: { required: true, content: { application/json: { schema: { $ref: '#/components/schemas/OutboundPick' } } } }
       responses: { '200': { description: 更新后的统一出库任务, content: { application/json: { schema: { $ref: '#/components/schemas/PdaOutboundTaskResponse' } } } }, '409': { description: 库存、数量或幂等冲突 } }
   /api/pda/v1/last-leg/outbound-tasks/{taskNo}/pallets/{palletNo}/pick:
     post:
-      summary: 扫描一件代发托盘并原子拣取整托剩余箱件
-      description: 仅适用于一件代发出库；按托盘汇总本任务内全部 SKU 和未拣箱唛，任一库存校验失败则整托回滚。
+      summary: 扫描出库托盘并原子拣取整托剩余箱件
+      description: 适用于一件代发、换标、仓储转运和退货整托出库；退货按每箱一条冻结明细核对整托全部预留箱、客户和状态，内容变化拒绝提交。任一库存校验失败则整托回滚。
       parameters:
         - { name: taskNo, in: path, required: true, schema: { type: string } }
         - { name: palletNo, in: path, required: true, schema: { type: string } }
       requestBody: { required: true, content: { application/json: { schema: { $ref: '#/components/schemas/IdempotentAction' } } } }
-      responses: { '200': { description: 整托拣货后的任务, content: { application/json: { schema: { $ref: '#/components/schemas/PdaOutboundTaskResponse' } } } }, '404': { description: 当前任务没有该托盘 }, '409': { description: 非一件代发、库存不足或幂等冲突 } }
+      responses: { '200': { description: 整托拣货后的任务, content: { application/json: { schema: { $ref: '#/components/schemas/PdaOutboundTaskResponse' } } } }, '404': { description: 当前任务没有该托盘 }, '409': { description: 出库类型不支持、托盘内容变化、库存不足或幂等冲突 } }
   /api/pda/v1/last-leg/outbound-tasks/{taskNo}/complete:
     post:
       summary: 完成一件代发出库任务