Refresh SignalR overview content for .NET 10 and remove obsolete browser-era guidance

[Copilot]

This updates the high-traffic SignalR overview article to align with current ASP.NET Core guidance for .NET 10. The page previously contained stale ES6 transpilation content and underrepresented newer SignalR capabilities introduced in .NET 9+.

• Feature and capability refresh

  • Expanded the core feature list with current scaling and diagnostics positioning.
  • Added .NET 9+ capabilities (AOT/trimming, polymorphic hub parameters, distributed tracing) with version gating via moniker blocks to avoid surfacing them on older views.

• 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  • Removed outdated ES6 include usage from this overview page.
  • Removed stale ES6-focused and training-module links from “Additional resources.”
  • Added direct links to current scaling and diagnostics docs.

• Metadata compliance

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

:::moniker range=">= aspnetcore-9.0"
* Supports trimming and native ahead-of-time (AOT) compilation for supported scenarios.
* Supports polymorphic type handling in hub methods.
* Supports distributed tracing with `ActivitySource` for SignalR hub server and .NET client.
:::moniker-end

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• learn.microsoft.com
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)