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.

docs/DESIGN.md

@@ -216,6 +216,9 @@ Also in force:
 - A single-select row of filter chips goes through `FilterChipGroup` (its options are `Chip`s).
 - A button that starts slow work shows `loading` (a spinner, `aria-busy`) and can't be pressed twice.
   [Nielsen #1]
+- **A glyph means one thing.** Play (▷) starts playback, or resumes a paused transfer; a retry is the
+  refresh arrow (`RefreshCw`); a reset or revert is the counter-clockwise arrow (`RotateCcw`). A failed
+  download's Retry had worn the Play glyph, which promised a video. [Nielsen #4]
 
 ## Surfaces and page chrome — _Decided_ (batch B)
 
@@ -613,3 +616,4 @@ pick a density step; it never changes the anatomy or loses an action. [Nielsen #
 | 2026-09-27 | Conformance check (S3g)                          | A four-step check before a UI change is done: primitive at a named rung, the chapter re-read, the rendered page measured by kind and look, every state seen                                                                                                                                                            | A reviewer's eye per sprint                                                                                                                                                                            | The S1 probe found 69 button looks; after S3 every control kind is drawn by its primitive, and the check keeps a new look from arriving unnoticed                                             |
 | 2026-09-27 | Segmented rung                                   | `SegmentedToggle` defaults to the toolbar rung (28, `text-xs`); 24 only for a panel's captioned match toggle                                                                                                                                                                                                           | The small default                                                                                                                                                                                      | Two toolbars had inherited 10px type from the default beside 28px buttons                                                                                                                     |
 | 2026-09-27 | Copy rule (S3g)                                  | One name per feature (the rail may shorten it); four verbs for four meanings; sentence case with the app's places capitalised; "…" when a command asks first; one-sentence messages without a stop; curly quotes; dates relative in lists with the exact minute on hover, three absolute forms; units from Intl, short | Word-for-word names everywhere; the verbs as they were; all lower case; no "…"; always a stop; always absolute dates; long or compact units                                                            | The copy survey found 7 EN and 6 HU double names, 22 Delete against 27 Remove, five date shapes and three spellings of a minute; the owner picked every recommended option                    |
+| 2026-09-27 | One glyph, one meaning (S4)                      | Play only for playback or resuming a paused transfer; Retry = `RefreshCw`; reset / revert = `RotateCcw`                                                                                                                                                                                                                | Retry drawn with Play                                                                                                                                                                                  | The first UI-review run (Downloads) found a failed row whose Retry showed ▷ in the row and its menu                                                                                           |

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" }),
             },
       ],