feat(tui): scroll long names in every list and page through popups and chat

The sideways keys the results had (h/l, arrows, 0 and $) now scroll a
transfer's file name and a query too, each list on its own. The browse tree
and the room list take Home/End, PgUp/PgDn and the vim jumps like the main
lists, and a chat log, room or private, pages back through its history and
holds its place while new messages arrive; what arrives meanwhile counts as
unread until the reader returns to the end.

website/src/pages/docs.tsx

@@ -36,7 +36,8 @@ const PANE_KEYS: readonly (readonly [string, string])[] = [
   ['w', 'hide the focused pane; the others widen'],
   ['↑ ↓ · j k', 'move a row in any list'],
   ['Home End · g G', 'first / last row'],
-  ['PgUp PgDn · ^u ^d', 'a page, or half a page'],
+  ['PgUp PgDn · ^u ^d', 'a page, or half a page; in a chat, back through the log'],
+  ['h l · ← →', 'scroll a long name or query sideways, 0 and $ to either end'],
 ]
 
 const ROOM_KEYS: readonly (readonly [string, string])[] = [