Fix scoped CSS hot reload for hosted Blazor WebAssembly

[Copilot]

dotnet watch launched on an ASP.NET Core host could crash while processing scoped CSS changes from its referenced Blazor WebAssembly project. Static-asset resolution used the server project instead of the client project that owns the CSS bundle.

• Static asset ownership

  • Track a watch process’s static-asset project separately from its launching project.
  • Associate hosted Blazor processes with the WebAssembly client project.

• Scoped CSS updates

  • Resolve client scoped-CSS bundles from the client static-assets manifest.
  • Deliver resulting updates through the running server’s browser-refresh connection.

• Regression coverage

  • Extend the hosted Blazor watch test asset with scoped CSS.
  • Verify editing it produces a static-asset update.

public override ProjectGraphNode LaunchingProject => serverProject;
public override ProjectGraphNode StaticAssetProject => clientProject;

• Fixes dotnet watch crashes with a FormatException when editing a scoped CSS file #54915

[azure-pipelines]

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