fix(downloads): Retry draws the refresh glyph, not Play (E28 S4)

The first UI-review run (Downloads) found a failed row whose Retry wore the
Play glyph in the row and its menu, promising a video. DESIGN.md gains
'a glyph means one thing' and a log row.

frontend/src/components/DownloadCenter.menu.dom.test.tsx

@@ -132,6 +132,22 @@ describe("DownloadCenter · the queue row", () => {
     ]);
   });
 
+  it("draws Retry as 'do it again', never the Play glyph (row and menu)", async () => {
+    mocks.jobs = [job(1, "error"), job(2, "paused")];
+    mount();
+    const glyph = (el: Element) => el.querySelector("svg")?.getAttribute("class") ?? "";
+    const retry = rowOf("Clip 1").querySelector('[aria-label="downloads.actions.retry"]')!;
+    expect(glyph(retry)).toContain("lucide-refresh-cw");
+    // A paused job resumes: that one keeps the transport glyph.
+    const resume = rowOf("Clip 2").querySelector('[aria-label="downloads.actions.resume"]')!;
+    expect(glyph(resume)).toContain("lucide-play");
+    await openMenu(() => fireEvent.contextMenu(rowOf("Clip 1")));
+    const row = screen
+      .getAllByRole("menuitem", { hidden: true })
+      .find((b) => b.textContent === "downloads.actions.retry")!;
+    expect(glyph(row)).toContain("lucide-refresh-cw");
+  });
+
   it("closes on a second press of the same '…'", async () => {
     mocks.jobs = [job(1, "running")];
     mount();

frontend/src/components/DownloadCenter.tsx

@@ -9,6 +9,7 @@ import {
   Play,
   PlayCircle,
   Plus,
+  RefreshCw,
   Settings2,
   Share2,
   UploadCloud,
@@ -225,7 +226,12 @@ export default function DownloadCenter() {
                           : "downloads.actions.resume",
                       )}
                     >
-                      <Play className="w-4 h-4" />
+                      {/* Retry is "do it again", not playback: the Play glyph promised a video. */}
+                      {job.status === "error" ? (
+                        <RefreshCw className="w-4 h-4" />
+                      ) : (
+                        <Play className="w-4 h-4" />
+                      )}
                     </IconBtn>
                   )}
                 </DownloadRow>

frontend/src/components/useDownloadActions.tsx

@@ -9,6 +9,7 @@ import {
   Pencil,
   Play,
   PlayCircle,
+  RefreshCw,
   RotateCcw,
   Scissors,
   Share2,
@@ -139,7 +140,7 @@ export function useDownloadActions({
               label: t(
                 job.status === "error" ? "downloads.actions.retry" : "downloads.actions.resume",
               ),
-              icon: icon(Play),
+              icon: icon(job.status === "error" ? RefreshCw : Play),
               onSelect: () => act.mutate({ id: job.id, op: "resume" }),
             },
       ],