Clean up Arch profile: remove i3/Void-specific config and fix GNOME integration

- Remove XFCE/i3-specific packages and dotfiles from Arch path (xarchiver,
  udiskie, Thunar, xfce-polkit, clipman, screenshooter)
- Separate per-OS dotfiles: mimeapps, udiskie config, GTK theme script,
  udiskie-password, dbus-session and ssh-agent fragments moved to Void-only
- Add mimeapps.arch.list with Nautilus/GNOME associations for nymph
- Move dunst/rofi directory creation from common to profile_desktop_i3
- Add gnome-keyring PAM hooks for GDM (gdm-password) in profile_desktop_gnome
- Remove ssh-agent.service from desktop_systemd_user_services on Arch;
  drop ssh-agent dependency and hardcoded socket from emacs.service
- Add ttf-hack-nerd to Arch font packages
- Fix rustup bootstrap: use rustup-init on Void, rustup toolchain install on Arch

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

ansible/inventory/group_vars/arch.yml

@@ -64,7 +64,6 @@ arch_desktop_common_packages:
   - brightnessctl
   - dex
   - pinentry
-  - udiskie
   - xdg-desktop-portal
   - xdg-desktop-portal-gtk
   - xdg-user-dirs
@@ -116,12 +115,12 @@ arch_profile_packages:
   - texlive-binextra
   - texlive-latex
   - texlive-latexextra
+  - ttf-hack-nerd
   - ttf-liberation
   - ttf-nerd-fonts-symbols
   - ctags
   - uv
   - virt-manager
-  - xarchiver
   - xournalpp
   - zstd
 
@@ -135,7 +134,6 @@ enabled_services:
   - ufw
 
 desktop_systemd_user_services:
-  - ssh-agent.service
   - emacs.service
   - syncthing.service
   - rclone-pcloud.service