fix(downloads): GIF review round 1 — shape, HDR, caps, audio, copy

- A GIF squares its pixels before the size, so an anamorphic source keeps
  its shown shape (a 720x480 DVD at 16:9 was 480x320).
- An editor GIF of an HDR upload is tonemapped, as a clip GIF is.
- The length caps are judged in whole milliseconds: a range exactly at a
  cap is no longer refused for a float hair over it.
- A GIF is made of a video only: an audio file is refused with its reason
  and the editor offers no GIF for it.
- A GIF clip keeps no audio track: the track neither splits its cache key
  nor fails it.
- The editor's GIF notes keep their live region mounted; one size reads
  as one ("about 1 MB"), none is shown with nothing kept; the size choices
  show their unit; a shared picture that fails to load says so.
- Copy: the two-sentence GIF notes keep their last stop (a copy-rule test
  now holds it); the English warns of "only a still picture".

frontend/src/features/player/ClipPanel.dom.test.tsx

@@ -14,7 +14,11 @@ vi.mock("react-i18next", async (importOriginal) => {
   const actual = await importOriginal<typeof import("react-i18next")>();
   return {
     ...actual,
-    useTranslation: () => ({ t: (k: string) => k, i18n: { language: "en" } }),
+    // A size option reads as its own words with its unit ("480 px"); every other text is its key.
+    useTranslation: () => ({
+      t: (k: string, o?: { n?: string }) => (k === "clip.gif.side" ? `${o?.n} px` : k),
+      i18n: { language: "en" },
+    }),
   };
 });
 
@@ -281,7 +285,7 @@ describe("ClipPanel GIF", () => {
     render(<Harness onClose={onClose} start={{ start: 100, end: 108 }} />);
     expect(screen.queryByRole("group", { name: "clip.gif.size" })).toBeNull();
     fireEvent.click(screen.getByRole("button", { name: "clip.formatGif" }));
-    fireEvent.click(screen.getByRole("button", { name: "320" }));
+    fireEvent.click(screen.getByRole("button", { name: "320 px" }));
     expect(enqueueClip).not.toHaveBeenCalled();
     fireEvent.click(screen.getByRole("button", { name: "clip.gif.make" }));
     await waitFor(() => expect(onClose).toHaveBeenCalled());
@@ -298,7 +302,9 @@ describe("ClipPanel GIF", () => {
   it("starts at the default size, and a video again sends no GIF", async () => {
     render(<Harness start={{ start: 100, end: 108 }} />);
     fireEvent.click(screen.getByRole("button", { name: "clip.formatGif" }));
-    expect(screen.getByRole("button", { name: "480" }).getAttribute("aria-pressed")).toBe("true");
+    expect(screen.getByRole("button", { name: "480 px" }).getAttribute("aria-pressed")).toBe(
+      "true",
+    );
     fireEvent.click(screen.getByRole("button", { name: "clip.formatVideo" }));
     fireEvent.click(screen.getByRole("button", { name: "clip.cut" }));
     await waitFor(() => expect(enqueueClip).toHaveBeenCalled());
@@ -333,7 +339,21 @@ describe("ClipPanel GIF", () => {
     expect(range()).toBe("100-120");
     expect(note()).toBe("clip.gif.noPreview");
     // 20 s at 640: up to about 32 MB, past the server's 30.
-    fireEvent.click(screen.getByRole("button", { name: "640" }));
+    fireEvent.click(screen.getByRole("button", { name: "640 px" }));
     expect(note()).toBe("clip.gif.mayFail");
   });
+
+  it("says one size, not a range of one, when both ends read the same", () => {
+    // 1 s at 480: 0.4–1.0 MB, both shown as 1.
+    render(<Harness start={{ start: 100, end: 101 }} />);
+    fireEvent.click(screen.getByRole("button", { name: "clip.formatGif" }));
+    expect(screen.getByText("clip.gif.estimateOne")).toBeTruthy();
+    expect(screen.queryByText("clip.gif.estimate")).toBeNull();
+    // 10 s: a range.
+    fireEvent.change(screen.getByRole("textbox", { name: "clip.out" }), {
+      target: { value: "1:50" },
+    });
+    fireEvent.keyDown(screen.getByRole("textbox", { name: "clip.out" }), { key: "Enter" });
+    expect(screen.getByText("clip.gif.estimate")).toBeTruthy();
+  });
 });