Mirror of nomarchy.system.gaming.enable. When on, injects a Hyprland
windowrulev2 = fullscreen, class:^(steam_app_).*$ so games launched
through Steam grab the whole screen instead of opening windowed.
Gated via lib.mkIf so the rule is absent when the option is off
(AGENT.md guardrail: features must be option-gated). The rule is
appended to wayland.windowManager.hyprland.extraConfig (types.lines)
so it composes cleanly with the existing source-line entry point in
features/desktop/hyprland/default.nix.
Closes the "Gaming - Hyprland window rule" Next-column roadmap row.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>