[docs] Add deprecation notices to GitHub Models integration docs

src/frontend/src/content/docs/integrations/ai/github-models/github-models-connect.mdx

@@ -19,6 +19,10 @@ import githubIcon from '@assets/icons/github-icon.png';
   data-zoom-off
 />
 
+:::caution[Integration deprecated]
+The GitHub Models service is **no longer available to new customers**. The `Aspire.Hosting.GitHub.Models` integration is sunset as of Aspire 13.5. All public APIs are marked `[Obsolete]` and the package no longer appears in `aspire add` output. The package will ship one final obsolete release on NuGet and will be removed entirely in a future version. For new and existing apps, use the [Azure AI Foundry integration](/integrations/cloud/azure/azure-ai-foundry/azure-ai-foundry-get-started/) instead, which provides access to a broad catalog of models — including OpenAI's GPT models — and supports local development with `RunAsFoundryLocal()`. See [microsoft/aspire#18402](https://github.com/microsoft/aspire/issues/18402) for details.
+:::
+
 This page describes how consuming apps connect to a GitHub Model resource that's already modeled in your AppHost. For the AppHost API surface — adding a model resource, API key parameters, organization configuration, and health checks — see [GitHub Models hosting integration](../github-models-host/).
 
 When you reference a GitHub Model resource from your AppHost, Aspire injects the connection information into the consuming app as environment variables. Your app can either read those environment variables directly — the pattern works the same from any language — or, in C#, use the Aspire client integrations for automatic dependency injection, health checks, and telemetry.

src/frontend/src/content/docs/integrations/ai/github-models/github-models-get-started.mdx

@@ -17,6 +17,10 @@ import githubIcon from '@assets/icons/github-icon.png';
   data-zoom-off
 />
 
+:::caution[Integration deprecated]
+The GitHub Models service is **no longer available to new customers**. The `Aspire.Hosting.GitHub.Models` integration is sunset as of Aspire 13.5. All public APIs are marked `[Obsolete]` and the package no longer appears in `aspire add` output. The package will ship one final obsolete release on NuGet and will be removed entirely in a future version. For new and existing apps, use the [Azure AI Foundry integration](/integrations/cloud/azure/azure-ai-foundry/azure-ai-foundry-get-started/) instead, which provides access to a broad catalog of models — including OpenAI's GPT models — and supports local development with `RunAsFoundryLocal()`. See [microsoft/aspire#18402](https://github.com/microsoft/aspire/issues/18402) for details.
+:::
+
 [GitHub Models](https://github.com/marketplace/models) provides access to a broad catalog of AI models — including OpenAI's GPT models, DeepSeek, Microsoft's Phi models, and more — through GitHub's infrastructure and your existing GitHub token. The Aspire GitHub Models integration lets you model a GitHub Model resource as a first-class resource in your AppHost, then hand the connection information to any consuming app — regardless of language.
 
 ## Why use GitHub Models with Aspire

src/frontend/src/content/docs/integrations/ai/github-models/github-models-host.mdx

@@ -17,6 +17,10 @@ import githubIcon from '@assets/icons/github-icon.png';
   data-zoom-off
 />
 
+:::caution[Integration deprecated]
+The GitHub Models service is **no longer available to new customers**. The `Aspire.Hosting.GitHub.Models` integration is sunset as of Aspire 13.5. All public APIs are marked `[Obsolete]` and the package no longer appears in `aspire add` output. The package will ship one final obsolete release on NuGet and will be removed entirely in a future version. For new and existing apps, use the [Azure AI Foundry integration](/integrations/cloud/azure/azure-ai-foundry/azure-ai-foundry-get-started/) instead, which provides access to a broad catalog of models — including OpenAI's GPT models — and supports local development with `RunAsFoundryLocal()`. See [microsoft/aspire#18402](https://github.com/microsoft/aspire/issues/18402) for details.
+:::
+
 This article is the reference for the Aspire GitHub Models hosting integration. It enumerates the AppHost APIs — with examples for both `AppHost.cs` and `apphost.mts` — that you use to model GitHub Model resources in your [`AppHost`](/get-started/app-host/) project.
 
 If you're new to the GitHub Models integration, start with the [Get started with GitHub Models integrations](/integrations/ai/github-models/github-models-get-started/) guide. For how consuming apps read the connection information this page exposes, see [Connect to GitHub Models](../github-models-connect/).

src/frontend/src/content/docs/whats-new/aspire-13-5.mdx

@@ -198,8 +198,10 @@ The following breaking changes are included in Aspire 13.5:
 
 3. **aspire ps --resources flag removed**: The `--resources` and `--include-hidden` flags have been removed from `aspire ps`, which now focuses on AppHost-level summaries. Use `aspire describe` for detailed resource data.
 
+4. **GitHub Models integration deprecated**: The GitHub Models service is no longer available to new customers, so the `Aspire.Hosting.GitHub.Models` integration is sunset as of Aspire 13.5. All public APIs are marked `[Obsolete]`, and the package no longer appears in `aspire add` output. One final obsolete release will ship on NuGet, and the package will be removed entirely in a future version. Migrate to the [Azure AI Foundry integration](/integrations/cloud/azure/azure-ai-foundry/azure-ai-foundry-get-started/) instead. See [microsoft/aspire#18402](https://github.com/microsoft/aspire/issues/18402) for details.
+
 <Aside type="caution" title="Review deprecated APIs">
-  Review your code for uses of `ServiceProvider` on hosting context types and `PublishAsConnectionString` extension methods. These will generate compiler warnings in Aspire 13.5 and may become harder errors in future releases.
+  Review your code for uses of `ServiceProvider` on hosting context types and `PublishAsConnectionString` extension methods. These will generate compiler warnings in Aspire 13.5 and may become harder errors in future releases. If you use the `Aspire.Hosting.GitHub.Models` integration, plan to migrate off it before the package is removed.
 </Aside>
 
 ## Known issues