fix(just): escape bash parameter expansion in global justfile

modules/system/justfile.nix

@@ -2,8 +2,6 @@
 
 let
   justfileText = ''
-    FORCE := "0"
-
     [no-cd]
     manage:
         $EDITOR ~/.config/home-manager/home.nix
@@ -31,17 +29,17 @@ let
         set -euo pipefail
 
         src="/etc/skel/.config/home-manager"
-        dst="${XDG_CONFIG_HOME:-$HOME/.config}/home-manager"
+        dst="''${XDG_CONFIG_HOME:-$HOME/.config}/home-manager"
 
         mkdir -p "$dst"
         chmod 700 "$dst" || true
 
         overwrite="0"
-        if [[ "${FORCE}" == "1" ]]; then
+        if [[ "''${FORCE:-0}" == "1" ]]; then
           overwrite="1"
         elif [[ -e "$dst/flake.nix" || -e "$dst/home.nix" ]]; then
           read -r -p "Home Manager files already exist in $dst. Overwrite? [y/N] " ans
-          case "${ans:-}" in
+          case "''${ans:-}" in
             y|Y|yes|YES) overwrite="1" ;;
             *) overwrite="0" ;;
           esac