Chat: stop a tall message silently un-pinning the reader

ddiff --git a/public/index.html b/public/index.html
iindex 9f4146e4..77803666 100644
---- a/public/index.html
++++ b/public/index.html
@@@ -5136,7 +5136,7 @@ curl -s https://openvibe.media/live/@Goosely/chat-insight.json | jq ".chat_insig
  <script src="/js/chat-shared.js?v=3" defer></script>
  <script src="/js/emotes.js?v=8" defer></script>
  <script src="/js/gif-picker.js?v=1" defer></script>
--<script src="/js/chat.js?v=81" defer></script>
++<script src="/js/chat.js?v=82" defer></script>
  <script src="/js/chat-autocomplete.js?v=1" defer></script>
  <script src="/js/channel-uploads.js?v=12" defer></script>
  <script src="/js/controls.js?v=8" defer></script>
ddiff --git a/public/js/chat.js b/public/js/chat.js
iindex 2ac97834..89fdc604 100644
---- a/public/js/chat.js
++++ b/public/js/chat.js
@@@ -3367,7 +3367,13 @@ function addChatMessage(msg) {
      // message nodes (memory + scroll/layout thrash). Mirrors the caps the cross-feed /
      // widget containers already have. Don't trim mid history-hydration.
      if (!_loadingHistory) {
--        while (container.children.length > MAIN_CHAT_MAX_MESSAGES) container.removeChild(container.firstChild);
++        while (container.children.length > MAIN_CHAT_MAX_MESSAGES) {
++            // Removing from the top shortens everything above the viewport, so a reader who has
++            // scrolled back sees the text jump upward. Give back exactly what we took.
++            const lost = container.firstChild.getBoundingClientRect().height;
++            container.removeChild(container.firstChild);
++            if (!_chatPinned) container.scrollTop = Math.max(0, container.scrollTop - lost);
++        }
      }
      if (chatSettings.autoScroll) {
          if (_loadingHistory) {
@@@ -5402,12 +5408,47 @@ let _chatUserScrolledUp = false;
  let _chatUnreadCount = 0;
  let _loadingHistory = false;
  
++/**
++ * Is the reader following the live edge?
++ *
++ * This used to be measured inside scrollChat(), which every caller runs AFTER appending the new
++ * message — so scrollHeight already counted the message being announced, and the distance from
++ * the bottom was inflated by that message's own height. Anything taller than 100px (a wrapped
++ * multi-line message, a reply header, a clip card, a GIF card, a goal-reached card) therefore
++ * classified a reader sitting exactly at the bottom as "scrolled up", and chat silently stopped
++ * following with an unread badge they never asked for. That is the single most-felt bug in a
++ * live-streaming product.
++ *
++ * Appending content does not fire a scroll event, so tracking the state from the scroll listener
++ * instead means the value scrollChat() reads is the one from before the append — the thing it
++ * actually wanted — with no need to pass anything through six call sites.
++ */
++let _chatPinned = true;
++function _watchChatPin(container) {
++    if (!container || container._ovPinWatch) return;
++    container._ovPinWatch = true;
++    const update = () => {
++        _chatPinned = container.scrollHeight - container.scrollTop - container.clientHeight < 100;
++        if (_chatPinned) {
++            _chatUserScrolledUp = false;
++            _chatUnreadCount = 0;
++            _hideChatNewMessagesIndicator();
++        } else {
++            _chatUserScrolledUp = true;
++        }
++    };
++    container.addEventListener('scroll', update, { passive: true });
++    update();
++}
++
  function scrollChat() {
      const { messages: container } = getChatEl();
      if (!container) return;
--    // Only auto-scroll if user is near the bottom
--    const nearBottom = container.scrollHeight - container.scrollTop - container.clientHeight < 100;
--    if (nearBottom) {
++    // Attach here rather than only on the cold-connect path: initChat() returns early when a
++    // stream goes live or offline, and that swaps the render container — which used to leave the
++    // new one with no listener at all, so scrolling back to the bottom never re-armed following.
++    _watchChatPin(container);
++    if (_chatPinned) {
          container.scrollTop = container.scrollHeight;
          _chatUserScrolledUp = false;
          _chatUnreadCount = 0;