Clarify Swashbuckle availability in .NET 9+ banner (#36273)

* Initial plan

* Clarify Swashbuckle availability banner for .NET 9+

Co-authored-by: wadepickett <[email protected]>

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Co-authored-by: Copilot <[email protected]>

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Added 2nd link

* Clarify OpenAPI and Swashbuckle usage in .NET 9

Updated note on OpenAPI support in .NET 9 and later, clarifying the status of Swashbuckle.

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---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: wadepickett <[email protected]>
Co-authored-by: Wade Pickett <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

aspnetcore/tutorials/getting-started-with-swashbuckle.md

@@ -5,7 +5,7 @@ description: Learn how to add Swashbuckle to your ASP.NET Core web API project t
 ms.author: wpickett
 monikerRange: ">= aspnetcore-3.1 <= aspnetcore-8.0"
 ms.custom: mvc
-ms.date: 8/27/2024
+ms.date: 10/27/2025
 uid: tutorials/get-started-with-swashbuckle
 ---
 # Get started with Swashbuckle and ASP.NET Core

aspnetcore/tutorials/getting-started-with-swashbuckle/includes/getting-started-with-swashbuckle8.md

@@ -2,7 +2,12 @@
 :::moniker range=">= aspnetcore-6.0 < aspnetcore-9.0"
 
 > [!NOTE]
-> Swashbuckle is not available in .NET 9 or later. For an alternative, see <xref:fundamentals/openapi/overview?view=aspnetcore-9.0&preserve-view=true>.
+> In .NET 9 and later, ASP.NET Core includes built-in OpenAPI support. Swashbuckle is no longer included by default, but it remains available as a community package you can add manually to ASP.NET Core projects targeting .NET 9 or later.
+> 
+> • To understand the built‑in OpenAPI features, see <xref:fundamentals/openapi/overview?view=aspnetcore-9.0&preserve-view=true>.  
+> • To add and use the Swagger UI provided by the `Swashbuckle.AspNetCore.SwaggerUI` package for interactive exploration or local ad‑hoc testing, see <xref:fundamentals/openapi/using-openapi-documents#use-swagger-ui-for-local-ad-hoc-testing>.
+>
+>The following instructions apply when using Swashbuckle with .NET versions earlier than 9.
 
 There are three main components to Swashbuckle: