Why Steam identified game a Spacewar?
For initialization of Steamworks API (for better support of Steam Deck in this case) game should be available in user library Valve allow use appid from Spacewar for Steamworks API intergration (https://partner.steamgames.com/doc/sdk/api/example) If this is disturbing you, so you can delete the libraries (lib/PLATFORM-ARCHITECTURE/[lib?]steam_api.[dll|dylib|so]) before launching the game