On a phone the live player keeps its 16:9 box from the first paint (channel CLS 0.166 to 0) (#329)

ddiff --git a/public/css/features/channel.css b/public/css/features/channel.css
iindex 668e4a44..492f4f2f 100644
---- a/public/css/features/channel.css
++++ b/public/css/features/channel.css
@@@ -684,6 +684,10 @@
      .ch-info-bar .ch-avatar { width: 32px; height: 32px; font-size: 0.85rem; }
  }
  @media (max-width: 768px) and (orientation: portrait) {
++    /* The player keeps its 16:9 box from the first paint, and a landscape stream fills it. With no ratio the box was 0 px
++       until the player's loader or first frame arrived, and everything below it jumped (real users: phone channel CLS
++       p75 0.257, 2026-10-23). A portrait stream (.is-vertical, from the video's own size) still takes its own height. */
++    .video-container:not(.is-vertical) { aspect-ratio: 16 / 9; }
      #video-element {
          object-fit: contain;
          max-height: 65vh;