feat(files): the Downloads page goes — the tray, a Storage tab and a Downloads settings tab take its place

- The Downloads module, its rail icon and badge are gone. A bookmark, the remembered page and an old
  history entry that name it land on Files (urlState.resolvePage); `g d` goes to Files too.
- Users page: a Storage tab — the disk in numbers, every user's use against their own limit with
  their file count, every user's downloads; aligned tables, one menu per row (edit / reset quota,
  open source, copy, the owner's quota). The admin storage rows carry quota + file count, the admin
  job list its owner.
- Settings: a Downloads tab — the download formats in one list (duplicate a built-in, edit or delete
  your own) and the site sign-ins, moved from Account.
- "View" on an added download, a clip or a converting upload opens the tray on that row (unfolded,
  back if closed; a finished one opens as a file; under a player it opens without taking focus).
- The download dialog opens on the format used last.
- DataTable: `pager={false}` for a short list, `cardRow` to give a lone "…" its own card line.
- Welcome and README speak of Files; a new Files screenshot.

frontend/src/lib/downloadQueue.ts

@@ -4,9 +4,9 @@ import { createStore } from "./store";
 // The download queue as this tab has watched it: which jobs it has seen finish. The tray shows them
 // ("Done · Open") until it is closed, and announces each once (the done notice).
 //
-// Watched where the queue is FETCHED, not in a component's effect: every reader of the queue (the
-// tray, the Downloads page) fetches through `fetchQueue`, so a finish is seen once whichever of them
-// polled, and nothing has to diff the previous render's data.
+// Watched where the queue is FETCHED, not in a component's effect: every reader of the queue fetches
+// through `fetchQueue`, so a finish is seen once whichever of them polled, and nothing has to diff the
+// previous render's data.
 
 /** The statuses a job leaves on its own: it is waiting, or working. */
 export const IN_FLIGHT: ReadonlySet<string> = new Set(["queued", "running", "paused"]);
@@ -14,6 +14,13 @@ export const IN_FLIGHT: ReadonlySet<string> = new Set(["queued", "running", "pau
 let lastSeen: Map<number, string> | null = null;
 const finished = createStore<QueueJob[]>([]);
 const unannounced = createStore<QueueJob[]>([]);
+const revealing = createStore<Reveal | null>(null);
+
+/** A job to show in the tray, asked for at `at` (ms). */
+export interface Reveal {
+  id: number;
+  at: number;
+}
 
 /** Note a fresh queue: a job that is done now and was not on the last look has just finished. The
  *  first look only learns what is there — a file finished before this tab opened is old news. */
@@ -51,9 +58,21 @@ export function takeUnannounced(): QueueJob[] {
   return list;
 }
 
+/** "View" on a job just started (a download, a clip, an upload still converting): the tray opens on
+ *  its row — unfolded, back if it was closed, the keyboard on the row. One the tray no longer lists
+ *  because it is done already opens as a file. */
+export const showInTray = (id: number): void => revealing.set({ id, at: Date.now() });
+
+/** The pending "View", until the tray has answered it. */
+export const useRevealing = (): Reveal | null => revealing.useValue();
+
+/** The tray answered the "View" (or the job is not in the queue at all). */
+export const doneRevealing = (): void => revealing.set(null);
+
 /** Forget what was watched (a test starts from a tab that has looked at nothing). */
 export function resetQueueWatch(): void {
   lastSeen = null;
   finished.set([]);
   unannounced.set([]);
+  revealing.set(null);
 }