Add IList<AITool>.Add(ResponseTool) / AsAITool extension methods

[stephentoub]

For someone that knows they're using an OpenAI Responses IChatClient, they can Add a ResponseTool directly into ChatOptions.Tools, rather than needing to go through RawRepresentationFactory.

Microsoft Reviewers: Open in CodeFlow

[stephentoub]

cc: @rogerbarreto, @markwallace-microsoft

[Copilot]

Pull Request Overview

This PR adds convenience extension methods to enable direct use of OpenAI ResponseTool objects with the Microsoft.Extensions.AI framework. It introduces methods to add ResponseTool instances to IList collections and wrap them as AITool objects.

Key changes:

• Added IList<AITool>.Add(ResponseTool) extension method for direct addition of ResponseTool to tool collections
• Added ResponseTool.AsAITool() extension method to wrap ResponseTool instances as AITool objects
• Added internal ResponseToolAITool wrapper class to bridge ResponseTool and AITool types

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
MicrosoftExtensionsAIResponsesExtensions.cs	Added extension methods for ResponseTool to AITool conversion
OpenAIResponsesChatClient.cs	Added internal ResponseToolAITool wrapper class and handling logic
OpenAIConversionTests.cs	Added unit tests for the new extension methods
OpenAIResponseClientTests.cs	Updated existing test to verify both raw and wrapped tool usage
CHANGELOG.md files	Updated changelog entries to document the new functionality

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