UiPath/CoreWF ? reverse-engineered prompt

Build me a .NET 6 library for running Windows Workflow Foundation style workflows, so I can define simple workflows in code or in XAML and execute them. I want the basic pieces like activities, sequences, and a way to invoke a workflow and see it run, plus support for loading XAML workflows from a string or file. It should work on regular .NET 6 and also on Windows, and it should feel usable from a normal C# app without needing the old full .NET Framework. If there are any missing pieces from the old workflow runtime that are hard to support, keep the scope practical and make the core experience work well first. Please set up the project so it builds cleanly, includes a simple hello world example, and use current docs online if you need to check anything.