preview: adding an emoji pack no longer downloads the whole pack. A picture is fetched the first time something draws it and kept in a cache you can size in Settings (8, 32 or 128 MB, 32 by default), the picker asks only for the cells it shows, and typing a shortcode asks a pack's host for nothing at all. 'Download every picture now' is there for going offline. An install already holding more than the budget is trimmed to it at first load.