Move to slnx

[jaredpar]

This is the modern solution format for .NET. The advantages are that it has a defined format and more resistant to merge conflicts. This is supported by all modern .NET Tools (VS and VS Code)

[Copilot]

Pull request overview

Migrates the .NET solution from the legacy .sln format to the newer XML-based .slnx format to improve structure stability and reduce merge conflicts.

Changes:

• Added a new dotnet/GitHub.Copilot.SDK.slnx solution definition referencing the SDK and test projects.
• Removed the existing dotnet/GitHub.Copilot.SDK.sln solution file.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
dotnet/GitHub.Copilot.SDK.slnx	Introduces the new .slnx solution structure with src/test folders and project references.
dotnet/GitHub.Copilot.SDK.sln	Removes the legacy .sln solution file previously used by tooling.

[Copilot]

With the .sln removed, repo workflows that run dotnet restore, dotnet format, and dotnet build from the ./dotnet directory rely on implicit solution/project discovery (e.g. .github/workflows/dotnet-sdk-tests.yml:56-70). dotnet CLI commonly does not recognize .slnx as a build entrypoint, so these commands may start failing with “couldn’t find a project or solution file”. To keep CI/dev flows working, either keep the .sln alongside the .slnx, or update the affected scripts/workflows to pass explicit project/solution arguments (e.g., target src/GitHub.Copilot.SDK.csproj / test/GitHub.Copilot.SDK.Test.csproj, and point dotnet format at the same).

[SteveSandersonMS]

Awesome, thanks!