Force-run with Steam, but only in Steam versions

Currently, the Higurashi mod does not force the Steam version of the game to run through Steam, effectively breaking integration with Steam if the game is not ran from inside the Steam UI. We have a way in the installer to check whether the game is the Steam version or not. This code should be either ported to C# and added as a conditional check to the Steam API calls, or the installer should assist the game with Steam detection (e.g. by creating a file that informs the game whether or not this is the Steam version of the game).

The issue mentions the installer has a way to detect the Steam version; locate that detection code. Then, either port it to C# to conditionally enable Steam API calls, or modify the installer to create a flag file. Check existing Steam API integration in the C# codebase to see where the conditional should be added. Verify the fix by testing the game's Steam integration when launched outside the Steam UI.

Escrito por el modelo de indexación a partir del texto del issue.