Migrate ComputeCssScope to IMultiThreadableTask

[OvesN]

Fixes dotnet/msbuild#14052
Migrate ComputeCssScope to IMultiThreadableTask

[Copilot]

Pull request overview

This PR updates the Static Web Assets scoped CSS build task metadata to indicate it can run as a multi-threadable MSBuild task.

Changes:

• Mark ComputeCssScope with [MSBuildMultiThreadableTask].

Comments suppressed due to low confidence (1)

src/StaticWebAssetsSdk/Tasks/ScopedCss/ComputeCssScope.cs:24

• The PR title/description says this task was migrated to IMultiThreadableTask, but the change only adds [MSBuildMultiThreadableTask] and the task still doesn’t implement IMultiThreadableTask (unlike other multi-threadable tasks in this repo, e.g. StaticWebAssetsGeneratePackagePropsFile). Either update the PR metadata to match, or implement IMultiThreadableTask here (including the required TaskEnvironment property).

[MSBuildMultiThreadableTask]
public class ComputeCssScope : Task
{
    [Required]
    public ITaskItem[] ScopedCssInput { get; set; }

    [Required]
    public string TargetName { get; set; }

    [Output]
    public ITaskItem[] ScopedCss { get; set; }