dialogs.rs: main's Displace-map prompt runs before the fallible confirm_command. filter_dialog.rs: main's ask_displace_map uses the new confirm_command signature; SMART_FILTER_SET_PARAMS stays for main's uses; a smart-filter edit without a "layer" param previews the active layer, as the command runs it (main's smart_displace_preview_uses_the_map_document).