fix(result): Result<T> hash collision

A success result wrapping a value whose GetHashCode is 0 (e.g. Result<int>
with 0) collides with a failure result, both hashing to 0.

src/request.result/Result.Equality.cs

@@ -181,7 +181,12 @@ public partial class Result<T> : IEquatable<Result<T>>, IEquatable<T>
 			return comparer.GetHashCode(result.Value);
 		}
 
-		return 0;
+		if (result is { IsSuccess: true, Value: null })
+		{
+			return 0;
+		}
+
+		return result.Error?.GetHashCode() ?? 0;
 	}
 }