feat(rofi): add visible window border

configs/nixos/modules/desktop/session/rofi.nix

@@ -24,8 +24,8 @@ in
   options.modules.desktop.session.rofi.enable = lib.mkEnableOption "the rofi launcher";
 
   config = lib.mkIf config.modules.desktop.session.rofi.enable {
-    home-manager.users.${config.user.name} = {
-      # No theme is set here: Stylix's rofi target supplies the Nord one.
+    home-manager.users.${config.user.name} = hm: {
+      # Stylix supplies the Nord theme.
       programs.rofi = {
         enable = true;
 
@@ -36,6 +36,11 @@ in
           modi = "drun";
           show-icons = false;
         };
+
+        theme.window = {
+          border = hm.config.lib.formats.rasi.mkLiteral "2px";
+          border-color = hm.config.lib.formats.rasi.mkLiteral "#FFFFFF";
+        };
       };
     };