android: hours on the library's count line, By format, Jump back in on the empty search

The desktop Library summary's hours on the phone's count line; a By format
order from the file stats (lossless by depth and rate first, then by
bitrate, the badge as the card's line); the empty Search page's Jump back
in — the last records played — as the desktop's empty search shows them.

src/mobile/HalfSheet.svelte

@@ -21,7 +21,7 @@
     import { note } from "./notice.svelte.js";
     import { fmtOf, albumFmt, fmtBytes, basename, dirname, longDur, mmss, titleFromName } from "./util.js";
 
-    const SORTS = [["added", "Recently added"], ["az", "A–Z"], ["artist", "By artist"], ["year", "By year"]];
+    const SORTS = [["added", "Recently added"], ["az", "A–Z"], ["artist", "By artist"], ["year", "By year"], ["format", "By format"]];
 
     /* the last sheet is kept through its slide down */
     let shown = $state(null);