.Net: Bug: Cannot disable parallel tool calling for OpenAIResponseAgent

[DeepAQ]

Describe the bug
ResponseCreationOptionsFactory overrides ParallelToolCallsEnabled to true, making it impossible to disable parallel tool calling for OpenAIResponseAgent.

Recently, Azure OpenAI responses API has a bug or behavior change that blocks parallel function calling. A temporary workaround is to disable parallel function calling, but it is being forced by SK.

Expected behavior
The ParallelToolCallsEnabled should not be overridden. There should be an option to enable/disable parallel tool calling.

Platform

• Language: C#
• Source: NuGet package version 1.66.0
• AI model: OpenAI:GPT-5
• IDE: Visual Studio
• OS: Windows

[markwallace-microsoft]

@DeepAQ Are you interested in contributing a fix for this?

[DeepAQ]

@markwallace-microsoft Sure, here is my pull request: #13275