Updated main.js to better manage Steam Input environment variables, explicitly initialize and shutdown Steam Input, and regularly pump Steam callbacks to ensure proper controller support. Enhanced README-STEAM.md with detailed instructions for configuring Steam Input on Windows, Linux, and Steam Deck, including guidance for software/app limitations and launch options.
Adds environment variable setup and early gamepad initialization to main.js and preload.js to ensure native controller support on Steam Deck and SteamOS. Updates README-STEAM.md and BIG_PICTURE_MODE.md with detailed instructions for disabling Steam Input emulation and troubleshooting. Introduces start-steamdeck.sh launcher script to automate environment configuration for Steam Deck users.