feat(design): players on touch and the C5 control set, restart on the card (E28 S3f2)

Plex player: a finger's tap on the picture only shows or hides the controls,
the hide timer starts with playback, a double-tap on a side third skips 10 s,
the seek bar is a 2.75rem touch-none hit area with its head shown on touch.
The row is play/pause, Back by position, Next only with a next item, mute,
time, tracks, a fixed ⋯ (settings, media info, stats, shortcuts, download)
and fullscreen; Stop, Restart and the ±10 s buttons are gone.

A started card shows the video card's Continue + Restart pair (one shared
MediaResumeButtons, beside the picture's button), and its menu lists the
restart; the player opens that item at 0 (fromStart). YouTube modal: the
description opens from an ⓘ, the queue arrows sit inside the screen.

frontend/src/lib/plexPlayerHooks.controls.dom.test.tsx

@@ -7,12 +7,13 @@ import { describe, it, expect, vi, afterEach, beforeEach } from "vitest";
 import { act, renderHook } from "@testing-library/react";
 import { useControlsVisibility } from "./plexPlayerHooks";
 
-const setup = () => {
-  const video = { paused: false } as HTMLVideoElement;
+const setup = (menuOpen = false) => {
+  const video = document.createElement("video");
+  Object.defineProperty(video, "paused", { configurable: true, value: false });
   return renderHook(() =>
     useControlsVisibility({
       barAutoHideRef: { current: true },
-      menuOpenRef: { current: false },
+      menuOpenRef: { current: menuOpen },
       videoRef: { current: video },
     }),
   );
@@ -44,4 +45,19 @@ describe("useControlsVisibility", () => {
     act(() => vi.advanceTimersByTime(100));
     expect(result.current.uiVisible).toBe(false);
   });
+
+  // C3: on touch nothing moves a mouse, so a tap toggles the bar and playback arms the timer.
+  it("toggle hides a shown bar at once and shows a hidden one", () => {
+    const { result } = setup();
+    act(() => result.current.toggle());
+    expect(result.current.uiVisible).toBe(false);
+    act(() => result.current.toggle());
+    expect(result.current.uiVisible).toBe(true);
+  });
+
+  it("a tap does not hide the bar under an open menu", () => {
+    const { result } = setup(true);
+    act(() => result.current.toggle());
+    expect(result.current.uiVisible).toBe(true);
+  });
 });