Disable SDDM Wayland for Hyprland stability; enable X11/modesetting and set LIBVA driver

[benhunter]

Motivation

• Keep SDDM on the X11 path to avoid startup stability issues with Hyprland compositors.
• Ensure an X11 path is available by enabling the X server and selecting a generic modesetting driver for Wayland/X compatibility.
• Force the Intel VA driver name to iHD for improved VAAPI behavior in Electron/other apps.

Description

• Set services.displayManager.sddm.wayland.enable = false and added a comment explaining the reason.
• Enabled the X server by adding services.xserver.enable = true while keeping the existing XKB layout configuration.
• Removed the nvidia.modesetting.enable = true line and added services.xserver.videoDrivers = [ "modesetting" ] instead.
• Added LIBVA_DRIVER_NAME = "iHD" to environment.sessionVariables.

Testing

• Ran nixos-rebuild switch against the updated configuration and it completed successfully.
• Queried the configuration with nixos-option services.displayManager.sddm.wayland.enable and received false as expected.
• Queried the configuration with nixos-option services.xserver.videoDrivers and received [ "modesetting" ] as expected.

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Codex Task