feat(问翻小宝): 增强帮助搜索与会话历史

关键改动：

- 增加问翻小宝会话历史记录规则与测试

- 优化帮助搜索、兜底建议和页面交互结构

- 更新帮助截图资产和截图采集脚本

Co-Authored-By: Codex GPT-5 <codex@openai.com>

apps/web/lib/wenfan-conversation-history.ts

@@ -0,0 +1,53 @@
+export type WenfanHistoryMessage = {
+  role: string;
+  content?: string;
+};
+
+export type WenfanConversationRecord<TMessage extends WenfanHistoryMessage> = {
+  id: string;
+  title: string;
+  messages: TMessage[];
+};
+
+const DEFAULT_CONVERSATION_TITLE = '新对话';
+
+function getConversationTitle<TMessage extends WenfanHistoryMessage>(messages: TMessage[]): string {
+  const firstQuestion = messages.find((message) => message.role === 'user' && message.content?.trim());
+  return firstQuestion?.content?.trim() || DEFAULT_CONVERSATION_TITLE;
+}
+
+export function createWenfanConversationRecord<TMessage extends WenfanHistoryMessage>(
+  id: string,
+  messages: TMessage[],
+): WenfanConversationRecord<TMessage> {
+  return {
+    id,
+    title: getConversationTitle(messages),
+    messages,
+  };
+}
+
+export function updateWenfanConversationRecord<TMessage extends WenfanHistoryMessage>(
+  records: WenfanConversationRecord<TMessage>[],
+  activeId: string | null | undefined,
+  messages: TMessage[],
+): WenfanConversationRecord<TMessage>[] {
+  if (!activeId) return records;
+
+  return records.map((record) =>
+    record.id === activeId
+      ? {
+          ...record,
+          title: getConversationTitle(messages),
+          messages,
+        }
+      : record,
+  );
+}
+
+export function deleteWenfanConversationRecord<TMessage extends WenfanHistoryMessage>(
+  records: WenfanConversationRecord<TMessage>[],
+  id: string,
+): WenfanConversationRecord<TMessage>[] {
+  return records.filter((record) => record.id !== id);
+}