Add defensive checks for interface name processing

Co-authored-by: linkdotnet <[email protected]>

Author: Copilot

src/bunit.generators.internal/Web.AngleSharp/WrapperElementGenerator.cs

@@ -1,4 +1,5 @@
 using Microsoft.CodeAnalysis;
+using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
@@ -10,7 +11,10 @@ internal static class WrapperElementGenerator
 {
 	internal static string GenerateWrapperTypeSource(StringBuilder source, INamedTypeSymbol elm)
 	{
-		var name = $"{elm.Name.Substring(1)}Wrapper";
+		// Element interface names start with 'I' (e.g., IElement -> ElementWrapper)
+		var name = elm.Name.Length > 1 && elm.Name.StartsWith("I", StringComparison.Ordinal)
+			? $"{elm.Name[1..]}Wrapper"
+			: $"{elm.Name}Wrapper";
 		var wrappedTypeName = elm.ToDisplayString(GeneratorConfig.SymbolFormat);
 
 		source.AppendLine("#nullable enable");

src/bunit.generators.internal/Web.AngleSharp/WrapperElementsGenerator.cs

@@ -110,7 +110,10 @@ private static void GenerateWrapperFactory(StringBuilder source, ImmutableArray<
 
 		foreach (var elm in elementTypes)
 		{
-			var wrapperName = $"{elm.Name.Substring(1)}Wrapper";
+			// Element interface names start with 'I' (e.g., IElement -> ElementWrapper)
+			var wrapperName = elm.Name.Length > 1 && elm.Name.StartsWith("I", StringComparison.Ordinal)
+				? $"{elm.Name[1..]}Wrapper"
+				: $"{elm.Name}Wrapper";
 			source.AppendLine($"\t\t{elm.FullyQualifiedName} e => new {wrapperName}(e, elementFactory),");
 		}