[temonk]

Moves the library to net10.0 + net11.0 and drops net8.0 / net9.0.

Target frameworks

• Directory.Build.props: DefaultTargetFrameworks changed to net10.0;net11.0. The AltaSoft.Choice package now ships lib/net10.0 and lib/net11.0.
• AltaSoft.Choice.Generator is unchanged (netstandard2.0).
• AltaSoft.Choice.Generator.SnapshotTests: now multi-targets net10.0;net11.0.
• AltaSoft.ChoiceGenerator.Tests: moved from net10.0 to net11.0 only.
• CI workflows install the 11.0.x and 10.0.x SDKs.

Why AltaSoft.ChoiceGenerator.Tests is single-target

The project uses Microsoft.XmlSerializer.Generator (SGEN) to pre-generate serializers. The package runs as a legacy DotNetCliToolReference tool, which the dotnet CLI can't resolve in multi-targeted projects. With multiple target frameworks, SGEN fails on every framework and only reports a build warning, while the tests still pass because XmlSerializer falls back to runtime generation. Keeping the project on a single framework (net11.0) keeps the SGEN step working.

Package versions (Directory.Packages.props)

• Microsoft.XmlSerializer.Generator 10.0.12 → 11.0.0
• Microsoft.NET.Test.Sdk 18.10.0 → 18.11.1
• xunit.runner.visualstudio 4.0.0 → 4.0.1
• coverlet.collector 10.0.1 → 10.1.0
• Microsoft.CodeAnalysis.* is already on the latest version (5.9.0).

Tests

• dotnet build: 0 errors. No new warnings; the same 17 warnings as main (IDE0005 / CS0618 in tests).
• AltaSoft.ChoiceGenerator.XmlSerializers.dll is generated (SGEN succeeds).
• dotnet test: all passing. ChoiceGenerator.Tests 117 on net11.0; SnapshotTests 7 on each of net10.0 and net11.0.

Docs

• README badge updated to .NET 10+.