feat: update to dotnet 10, with unit test fixes and some packages updates

[hikarisakamoto]

From the Contributing Guidelines:

• [] If adding a new feature, I discussed it's design in an issue first
• [X] I verified there are no code warnings emitted for my code
• [X] I've included a unit test, and all the unit tests are passing

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Title

Update to .NET 10 and refresh dependencies

Description

Align the solution with .NET 10, refresh Roslyn/NuGet/test dependencies, and expand coverage for locating the .NET 10 runtime/reference packs.

Changes Made

1. Updated to .NET 10

Switched all projects and test assets to target net10.0 Added global.json to pin SDK 10 and keep roll-forward behavior

2. Updated NuGet packages

Bumped Roslyn, NuGet client packages, Spectre.Console, System.* libraries, and OpenAI to current net10-compatible versions Updated test dependencies (xUnit, coverlet, Spectre.Console.Testing, System.IO.Abstractions.TestingHelpers) Added net10 runtime locator tests for global installs and NuGet fallbacks; updated evaluation/source-link expectations

Why These Changes?

.NET 10: Keep the project current with the latest SDK/runtime and

[waf]

Thank you! This looks great. I will get this merged/released later today.

[hikarisakamoto]

I will be out for the rest of the week, but I can look as soon as I get back, on why the build broke

[hikarisakamoto]

@waf / @WeihanLi , I will move this back to draft while I fix the issues encountered with the build locator update, if it takes too much time, I might leave it to a different issue and PR