UI: convert LXDE/GNOME/KDE submenus to _menu style (XFCE parity)

Replace _radiolist with the _menu pattern used by xfce_menu:
while-true loop, fixed numbered items array, Back option that
breaks the loop, and direct case dispatch to the unchanged
installers. Navigation is now consistent across all four desktop
submenus (select an option, return to the parent menu, re-enter
without re-triggering a one-shot selection).

- bash -n OK, shellcheck 0 warnings, BATS 36/0
- _radiolist helper kept in utils.sh for compatibility (no callers)

modules/desktops/desktop_gnome.sh

@@ -5,19 +5,23 @@
 # License GPL v3
 
 gnome_menu() {
+    while true; do
+        local -a gn_items=()
+        gn_items+=("1" "GNOME (Full Desktop)")
+        gn_items+=("2" "GNOME Core (Minimal Install)")
+        gn_items+=("3" "Back")
         local choice
-    choice=$(_radiolist "GNOME" \
+        choice=$(_menu "GNOME" \
             "Select an option:" $TUI_ALTO $TUI_ANCHO $TUI_ALTO_LISTA \
-        "1" "GNOME (Full Desktop)" OFF \
+            "${gn_items[@]}")
-        "2" "GNOME Core (Minimal Install)" OFF \
+        [ -z "$choice" ] && break
-        "3" "Back" OFF)
-    [ -z "$choice" ] && return 0
         clear
-    case "$(echo "$choice" | tr -d '"')" in
+        case "$choice" in
         1) _install_gnome_full ;;
         2) _install_gnome_core ;;
-    3) return 0 ;;
+        3) break ;;
         esac
+    done
 }
 
 _install_gnome_full() {

modules/desktops/desktop_kde.sh

@@ -6,19 +6,23 @@
 # License GPL v3
 
 kde_menu() {
+    while true; do
+        local -a kd_items=()
+        kd_items+=("1" "KDE Plasma (Full Desktop)")
+        kd_items+=("2" "KDE Plasma Desktop (Minimal)")
+        kd_items+=("3" "Back")
         local choice
-    choice=$(_radiolist "KDE Plasma" \
+        choice=$(_menu "KDE Plasma" \
             "Select an option:" $TUI_ALTO $TUI_ANCHO $TUI_ALTO_LISTA \
-        "1" "KDE Plasma (Full Desktop)" OFF \
+            "${kd_items[@]}")
-        "2" "KDE Plasma Desktop (Minimal)" OFF \
+        [ -z "$choice" ] && break
-        "3" "Back" OFF)
-    [ -z "$choice" ] && return 0
         clear
-    case "$(echo "$choice" | tr -d '"')" in
+        case "$choice" in
         1) _install_kde_full ;;
         2) _install_kde_minimal ;;
-    3) return 0 ;;
+        3) break ;;
         esac
+    done
 }
 
 _install_kde_full() {

modules/desktops/desktop_lxde.sh

@@ -5,17 +5,23 @@
 # License GPL v3
 
 lxde_menu() {
+    while true; do
+        local -a lx_items=()
+        lx_items+=("1" "LXDE (Full Desktop)")
+        lx_items+=("2" "LXDE Core (Minimal Install)")
+        lx_items+=("3" "Back")
         local choice
-    choice=$(_radiolist "LXDE" \
+        choice=$(_menu "LXDE" \
             "Select an option:" $TUI_ALTO $TUI_ANCHO $TUI_ALTO_LISTA \
-        "1" "LXDE (Full Desktop)" OFF \
+            "${lx_items[@]}")
-        "2" "LXDE Core (Minimal Install)" OFF)
+        [ -z "$choice" ] && break
-    [ -z "$choice" ] && return 0
         clear
-    case "$(echo "$choice" | tr -d '"')" in
+        case "$choice" in
         1) _install_lxde_full ;;
         2) _install_lxde_core ;;
+        3) break ;;
         esac
+    done
 }
 
 _install_lxde_full() {