tools: set char width to minimum to reduce right panel horizontal space

tools/widgets/spin_button_double.vala

@@ -48,6 +48,7 @@ namespace Crown
 
 			_x.value_changed.connect(on_value_changed);
 			_x.scroll_event.connect(on_scroll);
+			_x.set_width_chars(1);
 
 			add(_x);
 		}