Re-run the metadata probe against the .NET 11 final release

[gfraiteur]

The .NET 11 analysis was verified against Preview 7 and re-verified against release candidate 1. Both
produced identical results, with one exception that has not converged.

Re-run the probe against the final release and confirm:

1. Whether runtime async is enabled by default without <Features>runtime-async=on</Features>.
   Microsoft documentation says it is; neither Preview 7 nor release candidate 1 behaves that way.
   This is the single finding that could still move, and it governs the priority of the runtime
   async work.
2. Whether the C# 15 constructs still compile to the shapes recorded in the analysis: a union as a
   sealed struct implementing IUnion with [UnionAttribute], a closed hierarchy as an abstract
   class with [IsClosedTypeAttribute], and extension indexers using the <G>$ and <M>$ marker
   type layout.
3. Whether async iterators and async void methods still use classic state machines.
4. Whether <UseRuntimeAsync> is implemented in the final SDK. It is absent from the release
   candidate 1 SDK entirely.

Analysis: Documentation/DotNet11-CSharp15-Impact.md in postsharp/PostSharp.

— Claude for Gael