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/roles/profile_desktop_gnome/tasks/main.yml

@@ -16,3 +16,27 @@
     force: true
     owner: root
     group: root
+
+- name: Enable gnome-keyring PAM auth hook for GDM
+  tags: [gnome]
+  ansible.builtin.lineinfile:
+    path: /etc/pam.d/gdm-password
+    insertafter: '^auth\s+include\s+system-local-login$'
+    line: "auth       optional  pam_gnome_keyring.so"
+    state: present
+
+- name: Enable gnome-keyring PAM session hook for GDM
+  tags: [gnome]
+  ansible.builtin.lineinfile:
+    path: /etc/pam.d/gdm-password
+    insertafter: '^session\s+include\s+system-local-login$'
+    line: "session    optional  pam_gnome_keyring.so auto_start"
+    state: present
+
+- name: Enable gnome-keyring PAM password hook for GDM
+  tags: [gnome]
+  ansible.builtin.lineinfile:
+    path: /etc/pam.d/gdm-password
+    insertafter: '^password\s+include\s+system-local-login$'
+    line: "password   optional  pam_gnome_keyring.so use_authtok"
+    state: present