Filed locked after calling FileRef.CreateFromLocalFile

Using Export To Docx I want to delete the original PDF file after calling the following:

FileRef sourceFileRef = FileRef.CreateFromLocalFile();

After Creating PDF from local file. I want to delete the original file but a lock remains on the file.

When I try to delete the file with File.Delete, an exception is thrown that there is a lock on the file from another process.

I cannot dispose of the the FileRef and even after setting the object to null, the lock remains.

该 issue 提到了 FileRef.CreateFromLocalFile 和 File.Delete；首先使用 Export To Docx 流程重现该序列，并观察原始 PDF 何时仍处于锁定状态。完成的标准是：PDF 创建后可以删除原始文件而不会出现 lock 异常，并且已确定所需的 FileRef 清理行为。

由索引模型根据 Issue 内容生成。