Update SignalR overview content for .NET 10 with include-based version architecture

[Copilot]

Fixes #37025

This updates the high-traffic SignalR overview article to align with current ASP.NET Core guidance for .NET 10 and restructures versioning to follow the include-file architecture used by other SignalR articles.

• Feature and capability refresh

  • Expanded the current feature list with updated scaling and diagnostics positioning.
  • Kept .NET 9+ capabilities (AOT/trimming, polymorphic hub parameters, distributed tracing) in newer-version content.

• Transport and protocol clarity

  • Clarified that WebSockets is the preferred transport for performance.
  • Updated protocol text to explicitly call out JSON as default and link to MessagePack protocol guidance.

• Resource cleanup and link hygiene

  • Removed outdated ES6 guidance from latest-version content.
  • Removed stale ES6-focused and training-module links from latest-version additional resources.
  • Added direct links to current scaling and diagnostics docs.

• Versioning architecture change (per feedback)

  • Main article now represents latest content with monikered latest section:
    • aspnetcore/signalr/introduction.md
  • Prior versions are moved to include files appended at the end of the main article:
    • aspnetcore/signalr/introduction/includes/introduction-9.md (= aspnetcore-9.0)
    • aspnetcore/signalr/introduction/includes/introduction-2-8.md (>= aspnetcore-2.1 <= aspnetcore-8.0)
  • This replaces the prior inline single-block versioning approach and matches the signalr/configuration.md pattern.
  • Per follow-up review feedback, include headings were adjusted so the H1 renders only once from introduction.md, and include file names were normalized from introduction9.md to introduction-9.md and introduction2.1-8.md to introduction-2-8.md.

• Metadata compliance

  • Updated ms.date.
  • Added ai-usage metadata.

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Internal previews

📄 File	🔗 Preview link
aspnetcore/signalr/introduction.md	https://review.learn.microsoft.com/en-us/aspnet/core/signalr/introduction?branch=pr-en-us-37026
aspnetcore/signalr/introduction/includes/introduction-9.md	Included via aspnetcore/signalr/introduction.md preview
aspnetcore/signalr/introduction/includes/introduction-2-8.md	Included via aspnetcore/signalr/introduction.md preview

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Screenshot

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Internal previews

📄 File	🔗 Preview link
aspnetcore/signalr/introduction.md	Overview of ASP.NET Core SignalR

[wadepickett]

@copilot , Can you change the versioning structure so all versinioning is not in one file but instead relies on previous versions moved to and include file for introduction.md?

For example:

Rather than using moniker versioning inline to the topic use as an example the same moniker version architecture that is used by:
aspnetcore/signalr/configuration.md
Where the main article represents the latest relaased verion which would be .NET 10 that includes the whole article with the latset information up to .net 10 and include files are added on the end of the topic for previous versions.

Here is the example configuration include files for all previous versions for configuration.md:
aspnetcore/signalr/configuration/includesaspnetcore/signalr/configuration/includes

For this PR in the case of aspnetcore/signalr/introduction.md, the new signalr/introduction/includes/ directory would contain the range from >= aspnetcore-2.1' to <= aspnetcore-8.0' with a new filepathname for that range named signalr/introduction/includes/ introduction2.1-8.md and a new file for version 9 that includes the new version 9 edits witha filepath name of signalr/introduction/includes/ introduction9.md

[Copilot]

@copilot , Can you change the versioning structure so all versinioning is not in one file but instead relies on previous versions moved to and include file for introduction.md?

For example:
...

Implemented the requested include-based versioning structure in commit 133cdbc.

Changes made:

• Main article now carries latest content in a .NET 10 moniker block.
• Added aspnetcore/signalr/introduction/includes/introduction9.md for ASP.NET Core 9.
• Added aspnetcore/signalr/introduction/includes/introduction2.1-8.md for ASP.NET Core 2.1–8.
• Wired both include files at the end of aspnetcore/signalr/introduction.md, matching the signalr/configuration.md architecture.

[wadepickett]

@copilot , The moniker range for each file should not include # Overview of ASP.NET Core SignalR. That way it only shows up once in the renderd file for each version. So # Overview of ASP.NET Core SignalR would not be in the includes, but would be in the in the introduction.md file, witha moniker range right below # Overview of ASP.NET Core SignalR

[Copilot]

@copilot , The moniker range for each file should not include # Overview of ASP.NET Core SignalR. That way it only shows up once in the renderd file for each version. So # Overview of ASP.NET Core ...

Updated in commit f51ee62.

I removed # Overview of ASP.NET Core SignalR from both include files so the H1 renders only once from introduction.md, and kept the moniker range directly under the H1 in the main article.

[wadepickett]

@copilot , change the names for this include files and update links to from introduction.md
This file name:
/signalr/introduction/includes/introduction2.1-8.md)

Should be come this name:
/signalr/introduction/includes/introduction-2-8.md)

[Copilot]

@copilot , change the names for this include files and update links to from introduction.md
This file name:
/signalr/introduction/includes/introduction2.1-8.md)
...

Done in commit fbe0420.

I renamed the include file to ~/signalr/introduction/includes/introduction-2-8.md and updated the include link in introduction.md accordingly.

Screenshot: Unable to attach a rendered preview screenshot from this environment because external preview/GitHub pages are blocked, but the include path update is in the commit above.

[wadepickett]

@copilot,
Change this file name:
aspnetcore/signalr/introduction/includes/introduction9.md
to this:
aspnetcore/signalr/introduction/includes/introduction-9.md

and update links to it in introduction.md

[Copilot]

@copilot,
Change this file name:
aspnetcore/signalr/introduction/includes/introduction9.md
...

Done in commit 5c3465c.

I renamed the include file to aspnetcore/signalr/introduction/includes/introduction-9.md and updated the include reference in aspnetcore/signalr/introduction.md.

Screenshot: https://github.com/user-attachments/assets/61194f6e-4d7e-4f9d-b6bb-bfbdfda96999

[wadepickett]

Approved after several fixes.

[tdykstra]

Great work! I left Just one question for you.