fix(player): what is chosen on the player chrome is marked amber, not written in the accent

A light theme's accent as text on the always-dark chrome was 2.84:1 (Slate). `--chosen` is the
accent unless a scope names its own; `media-marks` (was media-focus) points it, with the focus
ring, at the media amber. A chosen track stays white with an amber tick (MenuCheck reads
`text-chosen`); a chosen settings tab or toggle is white with an amber underline (MEDIA_CHOSEN).
The theme contract test holds the token, the tick and the player components free of accent text.

frontend/src/components/PlayerModal.tsx

@@ -936,7 +936,7 @@ export default function PlayerModal({
               ref={stageRef}
               // The wheel over the video is its volume, even inside a stacked card that scrolls.
               data-wheel-volume=""
-              className={`player-stage media-focus relative aspect-video w-full bg-black overflow-hidden ${
+              className={`player-stage media-marks relative aspect-video w-full bg-black overflow-hidden ${
                 wide ? (clipOpen ? "rounded-tl-2xl" : "rounded-l-2xl") : "rounded-t-2xl"
               } ${maximized ? "player-stage--max" : ""}`}
             >
@@ -1009,7 +1009,7 @@ export default function PlayerModal({
               {(maximized || isFullscreen) && !clipDocked && (
                 <div
                   onClick={(e) => e.stopPropagation()}
-                  className="absolute inset-x-0 bottom-0 z-menu flex h-14 items-center justify-start gap-x-3 overflow-x-auto border-t border-white/10 bg-media-chrome/95 media-focus px-3 text-sm text-white"
+                  className="absolute inset-x-0 bottom-0 z-menu flex h-14 items-center justify-start gap-x-3 overflow-x-auto border-t border-white/10 bg-media-chrome/95 media-marks px-3 text-sm text-white"
                 >
                   {hasQueue && (
                     <>