CollapseLauncher/Hi3Helper.Sophon — reverse-engineered prompt

I want a small C# .NET library for working with HoYoverse Sophon downloads, like the system used by HoYoPlay for games such as Genshin Impact and Zenless Zone Zero.

Build it so another app can fetch a Sophon manifest, read and enumerate the files and chunks, dump manifest info to JSON, and download the needed chunks directly to disk. It should support fresh downloads, updates, preload downloads, patch assets, and comparing what is already installed so it only grabs what is needed. Please include a simple download speed limiter and make the download flow reliable, with cancellation, progress callbacks, and clear errors.

Keep it as a reusable library, not a full launcher. Add a few console test examples that show how to fetch manifest info, download a game package, and run an update or preload flow. Target modern .NET, but keep compatibility with older .NET Framework if practical. Look up current Sophon or HoYoPlay details online if you need to.