修复：后台恢复时消息暴刷，只渲染最后50条并插入省略提示

resources/js/chat-room/message-renderer.js

@@ -457,6 +457,9 @@ export function enqueueChatMessage(msg) {
     state.chatMessageFlushTimer = scheduleFlush(flushQueuedChatMessages);
 }
 
+/** 后台恢复时公屏最大渲染条数，避免暴刷 */
+const MAX_BURST_RENDER = 50;
+
 /**
  * 分批渲染待处理消息，给动画、输入和滚动留出主线程时间。
  */
@@ -466,6 +469,23 @@ export function flushQueuedChatMessages() {
 
     state.chatMessageFlushTimer = null;
 
+    // 大批量消息堆积（后台标签页恢复）时，丢弃早于 MAX_BURST_RENDER 的消息，
+    // 插入一条省略提示，避免用户一回来就看到满屏消息狂刷。
+    if (state.pendingChatMessages.length > MAX_BURST_RENDER + 20) {
+        const skipped = state.pendingChatMessages.length - MAX_BURST_RENDER;
+        state.pendingChatMessages.splice(0, skipped);
+
+        const container = state.container;
+        if (container) {
+            const notice = document.createElement("div");
+            notice.className = "msg-line msg-burst-notice";
+            notice.style.cssText =
+                "text-align:center;padding:6px 0;margin:4px 0;font-size:12px;color:#94a3b8;border-top:1px dashed #d1d5db;border-bottom:1px dashed #d1d5db;";
+            notice.textContent = `⏫ 省略了 ${skipped} 条未读消息`;
+            container.appendChild(notice);
+        }
+    }
+
     const batch = state.pendingChatMessages.splice(0, CHAT_MESSAGE_FLUSH_BATCH_SIZE);
     const renderBatch = createChatMessageRenderBatch();
     batch.forEach((msg) => appendMessage(msg, renderBatch));