fix(files): review round 1, the page — honest states, the keyboard, the tray's words

- A library past the list's cap is searched and sorted on the server; the count says "the newest".
- Each folder and each search opens on its first page (DataTable pageScope, useCardPager scope).
- A file dropped where the page takes none never reaches the browser (which would unload the app).
- The viewer's arrows wait while a layer opened from it is on top, and scroll a wide text line;
  a text shows its first 5000 lines and says where the rest is.
- Confirms name the file (no more "your downloads"); the asking menu rows end in "…".
- The tray names a running step beside its bar, shows a pause mark for paused work, polls slowly
  while only paused work waits, and forgets a finished file that was deleted.
- An unchanged rename sends nothing; a paste opens the download dialog only with nothing on top;
  the link box never replaces what was typed.
- Honest states: folders that failed to load, a file no longer there, the storage figure; the rail
  says "nothing downloaded" only when there is nothing.
- Focus after deleting the open folder and when the format form opens; the format name's label.
- ui/Meter (one danger line for both quota bars) and ui/RenameField in the platform layer.
- Copy fixes, stale comments and the speculative hub key; a contract test for the list's
  parameters; e2e: the Files page and the paste intake.

frontend/src/lib/useCardPager.ts

@@ -19,10 +19,17 @@ export function useCardPager<T>(
   reveal?: { seq: number; match: (row: T) => boolean } | null,
   /** The size picker's name — what the cards ARE (the channel manager's are "cards"). */
   sizeLabel?: string,
+  /** Which list `rows` are: another one (a folder, a search, a sort) starts at page one. */
+  scope?: string,
 ) {
   const { t } = useTranslation();
   const [size, setSize] = useState(() => parseCardSize(readAccount(sizeKey, null)));
   const [page, setPage] = useState(0);
+  const [scopeSeen, setScopeSeen] = useState(scope);
+  if (scope !== scopeSeen) {
+    setScopeSeen(scope);
+    setPage(0);
+  }
 
   // During render against the last seq seen, as in DataTable (seeded so a mount never jumps).
   const [revealSeen, setRevealSeen] = useState(reveal?.seq);