Merge pull request #1166 from adamhathcock/copilot/sub-pr-1165

Add [Obsolete] attribute to ReaderOptions.DefaultBufferSize for backward compatibility

src/SharpCompress/Readers/ReaderOptions.cs

@@ -5,6 +5,16 @@ namespace SharpCompress.Readers;
 
 public class ReaderOptions : OptionsBase
 {
+    /// <summary>
+    /// The default buffer size for stream operations.
+    /// This value (65536 bytes) is preserved for backward compatibility.
+    /// New code should use Constants.BufferSize instead (81920 bytes), which matches .NET's Stream.CopyTo default.
+    /// </summary>
+    [Obsolete(
+        "Use Constants.BufferSize instead. This constant will be removed in a future version."
+    )]
+    public const int DefaultBufferSize = 0x10000;
+
     /// <summary>
     /// Look for RarArchive (Check for self-extracting archives or cases where RarArchive isn't at the start of the file)
     /// </summary>