fix: 品牌下发审查修复（esc统一/语料中性化/穿越加固/反向断言动态化）

Co-Authored-By: Claude Code <noreply@anthropic.com>

static/js/chat.js

@@ -86,9 +86,12 @@ var chatBrandReady = (function () {
         var em = contactHref(emailAttr || b.email || "", "mail");
         if (emBtn) { if (em) emBtn.href = em; else emBtn.style.display = "none"; }
         if (b.placeholder) inputEl.placeholder = b.placeholder;
+        var firstMsg = document.querySelector("#messages .message");
+        var bubble = firstMsg && firstMsg.querySelector(".bubble");
         if (b.welcome) {
-            var bubble = document.querySelector("#messages .message .bubble");
             if (bubble) bubble.textContent = b.welcome;
+        } else if (firstMsg) {
+            firstMsg.style.display = "none"; // 空 welcome 不渲染空气泡(与挂件行为对齐)
         }
         if (Array.isArray(b.topics) && b.topics.length) {
             var grid = document.querySelector(".popular-topics-grid");
@@ -286,15 +289,8 @@ var chatBrandReady = (function () {
         }
     });
 
-    // Popular topics buttons(出厂模板的兜底话题;brand 下发后由 applyBrand
-    // 重建,这里的绑定覆盖"brand 失败"路径)
-    var topicBtns = document.querySelectorAll(".popular-topic-btn");
-    topicBtns.forEach(function (btn) {
-        btn.addEventListener("click", function () {
-            var topic = this.getAttribute("data-topic");
-            sendTopicMessage(topic);
-        });
-    });
+    // (出厂模板话题区为空——话题按钮只由 applyBrand 重建并自带绑定,
+    // 无静态兜底绑定段)
 
     // Task 10: 会话 key 租户化(cc_session_id_<slug>)——brand 落定(成功或
     // 失败,slug 回退 "default")后才读 key/连 WS,保证同浏览器多租户互不串