[Bug]:harnessAgent 配置ossAmount，agentRun沙箱销毁时，并没有把工作空间备份到oss中

```
HarnessAgent agent =
HarnessAgent.builder()
.name("skill-execution-hello")
.sysPrompt("You are a helpful skill executor.")
.model("dashscope:qwen-plus")
.workspace("/Users/yudaobin/Documents/agentscope-workspace")
.filesystem(new AgentRunFilesystemSpec()
.addOssMount(new AgentRunOssMountConfig()
.setBucketName("ydb-agentrun")
.setBucketPath("/agentrun")
.setEndpoint("http://oss-cn-hangzhou-internal.aliyuncs.com")
.setMountDir("/home/user/agentscope/workspace"))
.apiKey("xxx")
.accountId("xxx")
.region("cn-hangzhou")
.templateName("xx-xx-xx")
.mcpServerUrl("https://xxx.agentrun-data.cn-hangzhou.aliyuncs.com/templates/xx-xx-xx/mcp")
.sandboxIdleTimeoutSeconds(1200)
.isolationScope(IsolationScope.USER))
.memory(
MemoryConfig.builder()
.flushTrigger(MemoryConfig.FlushTrigger.never())
.build())
.build();
```
AgentRunSandbox 释放时，并没有把沙箱中工作空间备份到oss 目录 “/agentrun” 中