fix(player): the stacked layout's minimum width no longer clips the wide one

The 36rem floor guards the stacked layout's width/height feedback loop; the
wide side-panel card has no such loop, and on a short wide window the floor
made the video taller than the card, cutting off YouTube's control bar. The
floor now applies to the stacked layout only; e2e covers a 1400x380 window.

frontend/src/components/PlayerModal.dom.test.tsx

@@ -512,7 +512,7 @@ describe("PlayerModal — the side panel on a wide window", () => {
     expect(screen.queryByRole("button", { name: "player.description" })).toBeNull();
     // The row's width: the video at the window's height, plus the panel and the side strips.
     expect(card.parentElement!.style.maxWidth).toBe(
-      "calc(max(36rem, (100dvh - 3rem - 0px) * 16 / 9) + 20rem + 7rem)",
+      "calc((100dvh - 3rem - 0px) * 16 / 9 + 20rem + 7rem)",
     );
   });