Remove Arch/nymph path, restore nymph as Void desktop

Delete all Arch-specific files (packages_arch role, profile_desktop_gnome
role, arch.yml group_vars, nymph.yml host_vars, arch dotfiles). Revert
nymph to the void group in inventory, remove the arch play from site.yml,
and restore profile_desktop_host/tasks/nymph.yml to its pre-Arch state
(GRUB + NVIDIA + prime-run). Preserve Void improvements introduced
alongside Arch work (desktop_void_dotfiles, desktop_void_source_tools,
profile_desktop_i3 dir additions, void-specific conditions).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ansible/inventory/host_vars/nymph.yml

@@ -1,49 +0,0 @@
----
-hostname: nymph
-
-desktop_sessions_enabled:
-  - gnome
-
-desktop_default_session: gnome
-desktop_default_session_env: wayland
-
-host_kernel_cmdline: >-
-  rd.luks.uuid=1e15d159-5d05-4a1f-9639-ac200dff9f9c rootflags=subvol=@
-  apparmor=1 security=apparmor nouveau.modeset=0 nvidia-drm.modeset=1
-
-host_systemd_boot_esp_path: /boot
-host_systemd_boot_default: arch.conf
-host_systemd_boot_timeout: 3
-host_systemd_boot_console_mode: max
-host_systemd_boot_editor: false
-host_systemd_boot_entries:
-  - filename: arch.conf
-    title: Arch Linux
-    linux: /vmlinuz-linux
-    initrds:
-      - /intel-ucode.img
-      - /initramfs-linux.img
-    options: "{{ host_kernel_cmdline }}"
-  - filename: arch-fallback.conf
-    title: Arch Linux fallback
-    linux: /vmlinuz-linux
-    initrds:
-      - /intel-ucode.img
-      - /initramfs-linux-fallback.img
-    options: "{{ host_kernel_cmdline }}"
-
-host_packages:
-  - intel-ucode
-  - intel-media-driver
-  - libva-intel-driver
-  - mesa
-  - nvidia-open
-  - nvidia-settings
-  - nvidia-utils
-  - power-profiles-daemon
-  - upower
-  - vulkan-icd-loader
-  - vulkan-intel
-
-host_enabled_services:
-  - power-profiles-daemon