fix(ragflow): preserve final retry response body

[Ycymac]

变更说明

• 修复 RetryInterceptor 在返回最终重试响应前将其关闭的问题
• 使用响应所有权状态区分“交给调用方的响应”和“拦截器内部废弃的响应”
• 新增重试后仍返回 500 的回归测试，验证最终响应体可读取且请求次数正确

根因与修复

原实现会在 finally 中关闭所有非成功响应，包括已经准备返回给 retrieve() 的最终 5xx 响应。因此上层执行 response.body().string() 时会抛出 IllegalStateException: closed。

修复后，只有未交给调用方的响应会由拦截器关闭：重试过程中被替换的响应仍及时释放，而最终响应（包括 5xx）保持可读，并继续由调用方已有的 try-with-resources 负责关闭。

验证

• RAGFlowClientTest#testRetryKeepsFinalErrorResponseBodyReadable：通过（修复前可稳定复现 IllegalStateException: closed）
• RAGFlow 模块测试：97 个测试全部通过
• mvn spotless:check：88 个模块全部通过
• 仓库级 mvn test：已执行；在 agentscope-core 的 2 个既有符号链接测试处因 Windows 当前进程缺少 Files.createSymbolicLink 所需特权而停止（此前已执行 2268 个测试，0 failures、2 errors、8 skipped），与本次 RAGFlow 改动无关

Fixes #714

[CLAassistant]

All committers have signed the CLA.

[Ycymac]

CI 更新 / CI update:

Ubuntu 构建失败发生在与本 PR 无关的 agentscope-harness：HarnessAgentDynamicHookBuilderTest.disableDynamicSkills_freezesRepositoriesIntoStaticMiddleware 的断言已执行完成，但 JUnit 清理 @TempDir 时因 DirectoryNotEmptyException 报错（Harness 汇总为 812 tests、0 failures、1 cleanup error）。Windows 构建随后被矩阵 fail-fast 取消，并非自身测试失败。

本 PR 仅修改 RAGFlow client 及其回归测试；RAGFlow 模块 97/97、Spotless 88 个模块均已在本地通过。我尝试重跑 workflow，但外部贡献者没有该仓库的 Actions 重跑权限。烦请维护者协助 rerun CI。

The Ubuntu job failed during JUnit @TempDir cleanup in the unrelated agentscope-harness module (DirectoryNotEmptyException; 812 tests, 0 failures, 1 cleanup error). The Windows matrix job was then canceled by fail-fast. This PR only changes the RAGFlow client and its regression test; the RAGFlow module passes 97/97 locally. I do not have repository permission to rerun the workflow, so a maintainer rerun would be appreciated.

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...pe/core/rag/integration/ragflow/RAGFlowClient.java	80.00%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[Ycymac]

CI 更新：在不修改代码和提交 SHA（ac7c997a）的情况下，通过重新打开 PR 触发了新一轮 workflow。本轮 License、Module Sync、CLA、Codecov、Ubuntu 全量构建和 Windows 全量构建均已通过；本地单独重跑 HarnessAgentDynamicHookBuilderTest 也为 11/11 通过。

因此，首轮 DirectoryNotEmptyException 可确认为偶发的 Harness 临时目录清理问题，与本次 RAGFlow 重试状态判断改动无关。PR 现已转为 Ready for review。

CI update: a new workflow was triggered without changing the code or commit SHA (ac7c997a). License, module sync, CLA, Codecov, Ubuntu, and Windows checks all passed, and the focused local HarnessAgentDynamicHookBuilderTest passed 11/11.

This confirms that the initial DirectoryNotEmptyException was a transient Harness temporary-directory cleanup failure unrelated to this RAGFlow retry-state change. The PR is now ready for review.

[Copilot]

Pull request overview

This PR fixes RAGFlow retry handling so the final response (including terminal 5xx responses) remains open for the caller to read the body, preventing IllegalStateException: closed during response.body().string() in retrieve().

Changes:

• Adjust RetryInterceptor response-closing logic to avoid closing the response that will be returned to the caller (including final 5xx).
• Add a regression test to ensure the final error response body is readable after a retry and that the request count matches expectations.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
agentscope-extensions/agentscope-extensions-rag/agentscope-extensions-rag-ragflow/src/main/java/io/agentscope/core/rag/integration/ragflow/RAGFlowClient.java	Updates retry interceptor to preserve the final response for the caller instead of closing it in finally.
agentscope-extensions/agentscope-extensions-rag/agentscope-extensions-rag-ragflow/src/test/java/io/agentscope/core/rag/integration/ragflow/RAGFlowClientTest.java	Adds a regression test validating final 500 response body readability after a retry and verifying request count.

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[Ycymac]

已根据 review 中指出的重试边界补充修复（fcabde80）。

问题场景是：前一次尝试抛出 IOException，但最后一次尝试正常获得 HTTP 5xx 响应。原实现会在循环结束后再次检查历史 lastException，导致旧的传输异常覆盖最终 HTTP 响应，同时使调用方无法读取最终响应体。

本次采用最小修改：删除 lastException 的声明、赋值及循环后的抛出逻辑。最终一次请求如果仍发生 IOException，现有 catch 分支会直接抛出；如果最终获得 HTTP 响应（包括 5xx），则将该响应返回给上层读取并按状态码处理。

同时新增回归测试 testRetryReturnsFinalErrorResponseAfterEarlierIOException，确定性模拟 IOException -> 500，验证最终响应及响应体能够返回，并且响应不会被拦截器提前关闭。

验证结果：

• RAGFlowClientTest：38/38 通过
• RAGFlow 模块：98/98 通过
• Spotless：通过
• GitHub License、Module Sync、CLA、Ubuntu、Windows 和 Codecov 检查均已通过