feat(chat): add configurable streaming output

ai_knowledge_base_v2/apps/user-client/src/components/ChatMessage.vue

@@ -15,16 +15,47 @@ const markdown = new MarkdownIt({ breaks: true, html: false, linkify: true });
 
 const answer = computed(() => {
   if (props.role === "user") return props.content;
-  // 部分模型会产生嵌套 think 标签，使用贪婪匹配移除完整思考区，再清理流式残留标签。
-  let content = props.content.replace(/<think>[\s\S]*<\/think>/gi, "");
-  content = content.replace(/<think>[\s\S]*$/i, "");
-  content = content.replace(/<\/?think>/gi, "");
-  return content.trim();
+  return stripStreamingReasoning(props.content).replace(/^\s+/, "");
 });
 
-const renderedContent = computed(() =>
-  props.role === "assistant" ? markdown.render(answer.value) : answer.value,
-);
+const hasAnswer = computed(() => answer.value.trim().length > 0);
+
+const renderedContent = computed(() => {
+  if (props.role !== "assistant") return answer.value;
+  return hasAnswer.value ? markdown.render(answer.value) : "";
+});
+
+function stripStreamingReasoning(content: string) {
+  const lower = content.toLowerCase();
+  let visible = "";
+  let cursor = 0;
+  let reasoningDepth = 0;
+  while (cursor < content.length) {
+    const tagStart = content.indexOf("<", cursor);
+    if (tagStart === -1) {
+      if (reasoningDepth === 0) visible += content.slice(cursor);
+      break;
+    }
+    if (reasoningDepth === 0) visible += content.slice(cursor, tagStart);
+    const tail = lower.slice(tagStart);
+    const openTag = tail.match(/^<think(?:\s[^>]*)?>/);
+    if (openTag) {
+      reasoningDepth += 1;
+      cursor = tagStart + openTag[0].length;
+      continue;
+    }
+    const closeTag = tail.match(/^<\/think\s*>/);
+    if (closeTag) {
+      reasoningDepth = Math.max(0, reasoningDepth - 1);
+      cursor = tagStart + closeTag[0].length;
+      continue;
+    }
+    if ("<think".startsWith(tail) || "</think>".startsWith(tail)) break;
+    if (reasoningDepth === 0) visible += "<";
+    cursor = tagStart + 1;
+  }
+  return visible;
+}
 
 const displayTime = computed(() => {
   // 消息服务返回的是 UTC 无时区字符串，补齐时区后再按用户本地时间展示。