fix: Replace the question flow with a menu that turns components on and off

- Menu detects what is on and applies only the changes: SteamOS
  conversion, SteamOS theme, Steam Deck/Machine icons, single user mode,
  and Steam Machine support (only on Fremont hardware)
- Everything is reversible: KDE settings go through an undo journal
  (lib/state.sh), system files are restored from their backups
- Steam Machine support: LED driver, udev rule giving the user the LED
  files, steamos-manager for Steam's hardware settings; OpenRGB dropped
- Edit Plasma files only while plasmashell is stopped so it can't
  overwrite them
- README and AGENTS.md describe the menu, the component model and the
  test environment

lib/steam-desktop.sh

@@ -1,24 +1,14 @@
 #!/bin/bash
 # Steam in the Plasma desktop session: gamepad UI args, virtual keyboard,
-# autostart, and no screen locking (like SteamOS).
+# autostart. Part of the SteamOS conversion (gaming_enable/gaming_disable).
 # Sourced by setup-gamescope-boot.sh; not meant to be run on its own.
 
-setup_steam_desktop() {
-    # Step 8b: always runs.
+steam_enable() {
     info "Applying non-optional SteamOS environment & keyboard fixes..."
-    local steam_env_dir gs_env systemd_user_dir
+    local steam_env_dir systemd_user_dir
     steam_env_dir="$HOME/.config/environment.d"
     mkdir -p "$steam_env_dir"
 
-    # 1. Force Gamescope Steam to boot into Deck mode and load Deck glyphs
-    echo "STEAM_GAMEPADUI_ARGS=\"-gamepadui -steamos3\"" > "$steam_env_dir/99-gamescope-steam-glyphs.conf"
-    gs_env="$HOME/.config/gamescope-session/environment"
-    if [[ -d "$HOME/.config/gamescope-session" ]]; then
-        touch "$gs_env"
-        sed -i '/^STEAM_GAMEPADUI_ARGS=/d' "$gs_env"
-        echo "STEAM_GAMEPADUI_ARGS=\"-gamepadui -steamos3\"" >> "$gs_env"
-    fi
-
     # 2. Prevent KDE Wayland from blocking the virtual keyboard overlay
     echo "KWIN_IM_SHOW_ALWAYS=1" > "$steam_env_dir/99-kde-virtual-keyboard.conf"
 
@@ -54,70 +44,36 @@ EOF
     ok "Steam UI parameters and keyboard autostart deployed successfully."
 }
 
-setup_single_user() {
-    # With SINGLE_USER (chosen in step 1), like SteamOS: one user and no
-    # password prompts, since typing a password with a controller is
-    # miserable. Hides Lock / Switch User / Log Out
-    # everywhere (launcher, Meta+L, Ctrl+Alt+Del) and never locks on idle or
-    # resume; "Return to Gaming Mode" is the way out of the desktop. Declining
-    # restores KDE's defaults.
-    local action allow=true
-    [[ "$SINGLE_USER" == true ]] && allow=false
-    for action in lock_screen switch_user start_new_session; do
-        kwriteconfig6 --file kdeglobals --group "KDE Action Restrictions" --key "action/$action" "$allow"
-    done
-    if [[ "$allow" == false ]]; then
-        kwriteconfig6 --file kscreenlockerrc --group Daemon --key Autolock false
-        kwriteconfig6 --file kscreenlockerrc --group Daemon --key LockOnResume false
-        kwriteconfig6 --file kscreenlockerrc --group Daemon --key Timeout 0
-        # The action restriction hides Lock in menus but not the Meta+L
-        # shortcut; unbind it (format: current,default,description).
-        kwriteconfig6 --file kglobalshortcutsrc --group ksmserver --key "Lock Session" \
-            $'none,Screensaver\tMeta+L,Lock Session'
-        kwriteconfig6 --file kglobalshortcutsrc --group ksmserver --key "Log Out" \
-            'none,Ctrl+Alt+Del,Show Logout Screen'
-        set_launcher_leave_buttons single
-        ok "Screen locking, user switching and logging out disabled."
-    else
-        kwriteconfig6 --file kscreenlockerrc --group Daemon --key Autolock --delete
-        kwriteconfig6 --file kscreenlockerrc --group Daemon --key LockOnResume --delete
-        kwriteconfig6 --file kscreenlockerrc --group Daemon --key Timeout --delete
-        kwriteconfig6 --file kglobalshortcutsrc --group ksmserver --key "Lock Session" \
-            $'Screensaver\tMeta+L,Screensaver\tMeta+L,Lock Session'
-        kwriteconfig6 --file kglobalshortcutsrc --group ksmserver --key "Log Out" \
-            'Ctrl+Alt+Del,Ctrl+Alt+Del,Show Logout Screen'
-        set_launcher_leave_buttons default
-        ok "Keeping KDE's normal screen locking and user switching."
-    fi
+steam_disable() {
+    info "Removing Steam desktop autostart..."
+    systemctl --user disable --now steam-desktop-autostart.service 2>/dev/null
+    rm -f "$HOME/.config/systemd/user/steam-desktop-autostart.service" \
+        "$HOME/.config/environment.d/99-kde-virtual-keyboard.conf"
+    systemctl --user daemon-reload
+    ok "Steam desktop settings removed (takes full effect at next login)."
 }
 
-set_launcher_leave_buttons() {
-    # "single": only Sleep / Restart / Shut Down buttons in the launcher, no
-    # Session dropdown (that's where Log Out lives). Restricting the
-    # "logout" action instead would also hide Restart and Shut Down.
-    # "default": Plasma's own buttons.
-    local mode="$1" applet
-    for applet in $(plasma_applets org.kde.plasma.kickoff); do
-        local -a grp=(--file plasma-org.kde.plasma.desktop-appletsrc --group Containments
-            --group "${applet%%:*}" --group Applets --group "${applet#*:}"
-            --group Configuration --group General)
-        if [[ "$mode" == single ]]; then
-            kwriteconfig6 "${grp[@]}" --key primaryActions 3
-            kwriteconfig6 "${grp[@]}" --key systemFavorites 'suspend,reboot,shutdown'
-        else
-            kwriteconfig6 "${grp[@]}" --key primaryActions --delete
-            kwriteconfig6 "${grp[@]}" --key systemFavorites --delete
-        fi
-    done
-    if pgrep -u "$USER" -x plasmashell >/dev/null; then
-        local js
-        if [[ "$mode" == single ]]; then
-            js="w.writeConfig('primaryActions', 3); w.writeConfig('systemFavorites', 'suspend,reboot,shutdown');"
-        else
-            js="w.writeConfig('primaryActions', 0); w.writeConfig('systemFavorites', 'suspend,hibernate,reboot,shutdown');"
-        fi
-        qdbus6 org.kde.plasmashell /PlasmaShell org.kde.PlasmaShell.evaluateScript \
-            "panels().forEach(function (p) { p.widgets('org.kde.plasma.kickoff').forEach(function (w) { w.currentConfigGroup = ['General']; $js w.reloadConfig(); }); })" \
-            >/dev/null 2>&1 || true
+# "Steam Deck/Machine icons" menu item: Steam's gamepad UI in SteamOS 3
+# mode, which shows Steam Deck button glyphs in gaming mode.
+glyphs_status() {
+    [[ -f "$HOME/.config/environment.d/99-gamescope-steam-glyphs.conf" ]]
+}
+
+glyphs_enable() {
+    local gs_env="$HOME/.config/gamescope-session/environment"
+    mkdir -p "$HOME/.config/environment.d"
+    echo 'STEAM_GAMEPADUI_ARGS="-gamepadui -steamos3"' > "$HOME/.config/environment.d/99-gamescope-steam-glyphs.conf"
+    if [[ -d "$HOME/.config/gamescope-session" ]]; then
+        touch "$gs_env"
+        sed -i '/^STEAM_GAMEPADUI_ARGS=/d' "$gs_env"
+        echo 'STEAM_GAMEPADUI_ARGS="-gamepadui -steamos3"' >> "$gs_env"
     fi
+    ok "Steam Deck/Machine icons on (from the next gaming mode start)."
+}
+
+glyphs_disable() {
+    rm -f "$HOME/.config/environment.d/99-gamescope-steam-glyphs.conf"
+    [[ -f "$HOME/.config/gamescope-session/environment" ]] &&
+        sed -i '/^STEAM_GAMEPADUI_ARGS=/d' "$HOME/.config/gamescope-session/environment"
+    ok "Steam's default button icons are back (from the next gaming mode start)."
 }