Add breaking change documentation for AddAzureOpenAI role default changes

[IEvangelist]

Summary

Add breaking change documentation for AddAzureOpenAI role default changes.

Fixes #3936

---

Internal previews

📄 File	🔗 Preview link
docs/compatibility/9.4/add-azure-openai-default-changes.md	AddAzureOpenAI defaults to CognitiveServicesOpenAIUser instead of CognitiveServicesOpenAIContributor
docs/compatibility/9.4/index.md	Breaking changes in .NET Aspire 9.4
docs/compatibility/toc.yml	docs/compatibility/toc

[Copilot]

Pull Request Overview

This PR adds documentation for a new behavioral breaking change in .NET Aspire 9.4, detailing the updated default role for AddAzureOpenAI.

• Introduce a TOC entry for the new breaking change
• Update the 9.4 index to list the new documentation
• Add add-azure-openai-default-changes.md with guidance on the role change

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
docs/compatibility/toc.yml	Add new TOC item for the AddAzureOpenAI default role change
docs/compatibility/9.4/index.md	Add a table row linking to the new breaking change doc
docs/compatibility/9.4/add-azure-openai-default-changes.md	Create doc detailing the role default change and its impact

Comments suppressed due to low confidence (5)

docs/compatibility/toc.yml:16

• The new TOC entry is only indented by 4 spaces, but it should be indented under the parent items: block (8 spaces total) to maintain valid YAML nesting.

    - name: AddAzureOpenAI defaults to CognitiveServicesOpenAIUser role

docs/compatibility/9.4/index.md:21

• [nitpick] Consider adding the definite article for clarity: change to "defaults to the CognitiveServicesOpenAIUser role".

| [AddAzureOpenAI defaults to CognitiveServicesOpenAIUser role](add-azure-openai-default-changes.md) | Behavioral change | 9.4 |

docs/compatibility/9.4/add-azure-openai-default-changes.md:25

• [nitpick] This section doesn’t use a heading; consider using ## Example (or ### Example) above the code block to match the other sections and improve structure.

Example:

docs/compatibility/9.4/add-azure-openai-default-changes.md:28

• Verify that Azure.Provisioning.CognitiveServices is the correct namespace for AddAzureOpenAI and CognitiveServicesBuiltInRole; if not, update it to the appropriate namespace (e.g., Azure.ResourceManager.CognitiveServices).

using Azure.Provisioning.CognitiveServices;

docs/compatibility/9.4/add-azure-openai-default-changes.md:52

• [nitpick] It might be clearer to include the method signature or parentheses (e.g., AddAzureOpenAI(...)) so readers know this is an extension method and can distinguish overloads.

- `Aspire.Hosting.AzureOpenAIExtensions.AddAzureOpenAI`

[eerhardt]

LGTM. Thanks