‼️🔴𝐋 Linux support for the launcher and the editor

While Avalonia supports Windows, Linux and MacOS, our code has some dependencies or assumptions of a Windows machine running the editor.

The purpose of this task is to identify all blocking points, fix issues or find alternatives in case it has to be done on a per-platform basis.

This task should cover both the launcher and the editor. It might be split into several sub-tasks if necessary.

Here is a non-exhaustive list of areas that are impacted by platform specifics:

• hard dependencies, prerequisites that might be necessary to install before the launcher or the game studio can be used on Linux or on MacOS
• file system and file path management (e.g. the path separator character is different: /vs \)
• nuget packages location and restore
• lack of Windows registry on other platforms

Start by auditing the launcher and editor for the platform-specific areas named in the issue: prerequisites, file paths, NuGet restore locations, and Windows Registry usage. Determine which blockers affect Linux or macOS and whether they need alternatives or per-platform handling. Done means both the launcher and editor can be used on Linux, with the remaining platform-specific work clearly split into sub-tasks if necessary.