Document .NET 11 ChangeToken.OnChange async-overload rebinding behavior

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In .NET 11 Preview 7, new ChangeToken.OnChange async overloads (Func<Task> / Func<TState, Task>) can silently change overload resolution for existing async/Task callbacks after recompilation. The docs now explicitly describe the behavioral shift from async void-style fire-and-forget semantics to task-completion-based re-registration.

• New breaking-change article (.NET 11 / Extensions)

  • Added docs/core/compatibility/extensions/11/changetoken-onchange-async-overloads-rebind-callbacks.md.
  • Captures prior vs. new binding behavior, runtime impact (re-registration timing, callback coalescing, exception flow), reason for change, and migration guidance.

• Compatibility navigation and index updates

  • Added the new entry to:
    • docs/core/compatibility/11.md (Extensions table)
    • docs/core/compatibility/toc.yml (.NET 11 > Extensions)

• Related primitives doc update

  • Updated docs/core/extensions/primitives.md to reflect that ChangeToken.OnChange consumers can now be synchronous (Action / Action<TState>) or asynchronous (Func<Task> / Func<TState, Task>).

// .NET 11 now binds this to Func<Task> overload (async Task), not Action (async void).ChangeToken.OnChange(config.GetReloadToken,async()=>{awaitTask.Delay(1000);Console.WriteLine("Reloaded");});

• Fixes[Breaking change]: ChangeToken.OnChange async overloads change binding of existing async/Task-returning callbacks #54635

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Internal previews

File	Preview link
docs/core/compatibility/11.md	docs/core/compatibility/11
docs/core/compatibility/extensions/11/changetoken-onchange-async-overloads-rebind-callbacks.md	docs/core/compatibility/extensions/11/changetoken-onchange-async-overloads-rebind-callbacks
docs/core/compatibility/toc.yml	docs/core/compatibility/toc
docs/core/extensions/primitives.md	docs/core/extensions/primitives

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