Migrate to SLNX

[shibayan]

This pull request updates several third-party dependencies across the solution to their latest versions, focusing on both application and test projects. The changes aim to keep the codebase current with security patches and new features, and to ensure compatibility with the latest tooling.

Dependency updates:

Application dependencies:

• Upgraded Microsoft.Extensions.DependencyInjection from 9.0.4 to 9.0.8 in WinQuickLook.App and updated its lockfile accordingly. [1] [2]
• Updated Markdig from 0.41.1 to 0.41.3 and Microsoft.Web.WebView2 from 1.0.3179.45 to 1.0.3405.78 in both WinQuickLook.Core and WinQuickLook.App, including all relevant lockfiles. [1] [2] [3] [4]

Test dependencies:

• Upgraded test-related packages in WinQuickLook.Core.Tests, including Microsoft.NET.Test.Sdk (17.13.0 → 17.14.1), xunit.runner.visualstudio (3.0.2 → 3.1.4), Xunit.StaFact (2.1.7 → 3.0.13), and xunit.v3 (2.0.1 → 3.0.1), with all transitive dependencies updated in the lockfile. [1] [2] [3] [4] [5] [6]

Other changes:

• The solution file WinQuickLook.sln was removed, possibly to be replaced or regenerated.

[Copilot]

Pull Request Overview

This pull request migrates the solution from the traditional .sln format to the modern .slnx (XML-based solution) format and updates multiple NuGet package dependencies to their latest versions.

Key changes:

• Replace WinQuickLook.sln with WinQuickLook.slnx for modern XML-based solution format
• Update application dependencies including Microsoft.Extensions.DependencyInjection (9.0.4 → 9.0.8), Markdig (0.41.1 → 0.41.3), and Microsoft.Web.WebView2 (1.0.3179.45 → 1.0.3405.78)
• Upgrade test framework dependencies with major version updates for xunit packages (v2 → v3) and Microsoft.NET.Test.Sdk (17.13.0 → 17.14.1)

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
WinQuickLook.slnx	New XML-based solution file replacing the traditional .sln format
WinQuickLook.sln	Removal of the legacy solution file
WinQuickLook.Core/WinQuickLook.Core.csproj	Updated Markdig and Microsoft.Web.WebView2 package versions
WinQuickLook.Core/packages.lock.json	Updated lockfile reflecting new package versions for Core project
WinQuickLook.Core.Tests/WinQuickLook.Core.Tests.csproj	Major updates to test framework packages (xunit v2 → v3, test SDK updates)
WinQuickLook.Core.Tests/packages.lock.json	Updated lockfile with new test dependencies and transitive dependencies
WinQuickLook.App/WinQuickLook.App.csproj	Updated Microsoft.Extensions.DependencyInjection package version
WinQuickLook.App/packages.lock.json	Updated lockfile reflecting dependency injection package update

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}