Move to .NET 11 RC1 and refresh packages

[Agash]

• Formats with CSharpier and checks it in CI.
• Moves to the .NET 11 RC1 SDK; samples and tools target net11.0.
• Test and sample projects generate docs, so IDE0005 runs there too.
• Refreshes packages.
• Doc example builds get a directory per framework; the two test hosts raced on the same files.
• dotnet test gets --project/--solution explicitly; the RC1 SDK resolves a nested relative project path twice, so nested paths are absolute.