Remove custom OpenAI code with official library

Author: waf

CSharpRepl.Services/CSharpRepl.Services.csproj

@@ -19,6 +19,7 @@
     <PackageReference Include="Microsoft.Extensions.Caching.Memory" Version="9.0.0" />
     <PackageReference Include="Microsoft.Extensions.DependencyModel" Version="9.0.0" />
     <PackageReference Include="Microsoft.SymbolStore" Version="1.0.555801" />
+    <PackageReference Include="OpenAI" Version="2.1.0" />
     <PackageReference Include="PrettyPrompt" Version="4.1.1" />
     <PackageReference Include="Spectre.Console.Cli" Version="0.49.1" />
     <PackageReference Include="System.IO.Abstractions" Version="21.1.3" />

CSharpRepl.Services/Completion/AutoCompleteService.cs

@@ -51,7 +51,7 @@ public async Task<CompletionItemWithDescription[]> Complete(Document document, s
                 .ConfigureAwait(false);
 
             var completionsWithDescriptions = completions?.ItemsList
-                .Where(item => !(item.IsComplexTextEdit && item.InlineDescription.Length > 0)) //TODO https://github.com/waf/CSharpRepl/issues/236
+                .Where(item => item.DisplayText != nameof(__CSharpRepl_RuntimeHelper) && !(item.IsComplexTextEdit && item.InlineDescription.Length > 0)) //TODO https://github.com/waf/CSharpRepl/issues/236
                 .Select(item => new CompletionItemWithDescription(item, GetDisplayText(item), cancellationToken => GetExtendedDescriptionAsync(completionService, document, item, highlighter)))
                 .ToArray() ?? [];