Remove i3 desktop profile and st terminal

Elimina completamente la sessione desktop i3 (X11), ormai non più usata
(gli host espongono solo sway e Hyprland su Wayland):
- ruolo profile_desktop_i3 e voce emptty i3.desktop
- desktop_i3_packages e i guard 'i3' in desktop_sessions_enabled
- desktop_i3_dotfiles e host_i3_dotfiles (autorandr X11)
- dotfiles i3/X11: .xinitrc, i3, i3blocks, picom, polybar, autorandr
- task host-specifici i3 (copy dotfiles, wrap prime-run su nymph)
- rimuove st (terminale X11 da sorgente) da desktop_void_source_tools
- consolida lo script live in scripts/remove_i3.sh, elimina cleanup-i3.sh
- aggiorna la documentazione (README/AGENTS/CLAUDE/knowledge)

Config Emacs lasciata invariata di proposito.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ansible/roles/profile_desktop_host/tasks/nymph.yml

@@ -53,11 +53,3 @@
     group: "{{ user_group }}"
     mode: "0755"
     force: false
-
-- name: Wrap alacritty with prime-run for NVIDIA PRIME offload
-  tags: [nvidia, dotfiles, dotfiles:desktop, dotfiles:host]
-  ansible.builtin.lineinfile:
-    path: "{{ user_home }}/.config/i3/config"
-    regexp: '^bindsym \$mod\+Return exec --no-startup-id /usr/bin/alacritty'
-    line: 'bindsym $mod+Return exec --no-startup-id ~/.local/bin/prime-run /usr/bin/alacritty'
-  when: "'i3' in (desktop_sessions_enabled | default([]))"