Fix CS0136 compile error: remove duplicate 'defaultValue' declaration in else branch

The outer 'if (node.Default != null)' block already declares 'defaultValue' on
line 449. The branch's new else-branch code was incorrectly redeclaring it, causing
CS0136: A local variable named 'defaultValue' is already defined in this scope.
Fix: remove the redundant declaration in the else branch and reuse the existing one.

https://claude.ai/code/session_01AkwUvu3XuCdj3D4axoX4UX

Author: claude

CodeConverter/CSharp/ExpressionNodeVisitor.cs

@@ -476,7 +476,6 @@ public override async Task<CSharpSyntaxNode> VisitParameter(VBSyntax.ParameterSy
                 attributes.Insert(0,
                     CS.SyntaxFactory.AttributeList(CS.SyntaxFactory.SeparatedList(optionalAttributes)));
             } else {
-                var defaultValue = node.Default.Value.SkipIntoParens();
                 var paramSymbol = _semanticModel.GetDeclaredSymbol(node) as IParameterSymbol;
                 if (paramSymbol?.Type?.SpecialType == SpecialType.System_String &&
                     _semanticModel.GetTypeInfo(defaultValue).Type?.SpecialType == SpecialType.System_Char) {