fix(chat): normalize message date headers

src/data/dto/chat/ui_message.ts

@@ -10,7 +10,7 @@ import { z } from "zod";
 export const UiMessageSchema = z.object({
   content: z.string(),
   isFromAI: z.boolean(),
-  /** 显示用时间戳（HH:mm） */
+  /** 日期分隔条使用的本地日期（YYYY-MM-DD） */
   date: z.string(),
   /** 图片 URL（base64 data URL 或 http URL） */
   imageUrl: z.string().optional(),

src/stores/chat/chat-machine.helpers.ts

@@ -25,7 +25,7 @@ import { chatRepository } from "@/data/repositories/chat_repository";
 import type { IChatRepository } from "@/data/repositories/interfaces";
 import { ChatStorage } from "@/data/storage/chat/chat_storage";
 import { ChatSendResponse } from "@/data/dto/chat/chat_send_response";
-import { formatDate, Result, Logger } from "@/utils";
+import { todayString, Result, Logger } from "@/utils";
 
 import type { ChatState } from "./chat-state";
 
@@ -61,10 +61,16 @@ export function localMessagesToUi(
   return records.map((m) => ({
     content: m.content,
     isFromAI: m.role === "assistant",
-    date: m.createdAt,
+    date: messageDateFromCreatedAt(m.createdAt),
   }));
 }
 
+function messageDateFromCreatedAt(createdAt: string): string {
+  const parsed = new Date(createdAt);
+  if (Number.isNaN(parsed.getTime())) return todayString();
+  return todayString(parsed);
+}
+
 /**
  * ChatSendResponse → UiMessage（纯函数）
  * - 业务事实：后端响应就是 AI 的回复
@@ -74,7 +80,7 @@ export function sendResponseToUiMessage(response: ChatSendResponse): UiMessage {
   return {
     content: response.reply,
     isFromAI: true,
-    date: formatDate(new Date(response.timestamp)),
+    date: todayString(new Date(response.timestamp)),
   };
 }
 
@@ -201,7 +207,7 @@ export async function readAndSyncHistory(): Promise<{
       "there were things I couldn't say there. " +
       "Finally I can relax. How was your day out?",
     isFromAI: true,
-    date: formatDate(),
+    date: todayString(),
   };
 
   // 1. 读 local

src/stores/chat/chat-machine.ts

@@ -38,7 +38,7 @@
 import { setup, assign } from "xstate";
 
 import { ChatStorage } from "@/data/storage/chat/chat_storage";
-import { formatDate, todayString, Logger } from "@/utils";
+import { todayString, Logger } from "@/utils";
 
 import { ChatState, initialState } from "./chat-state";
 import type { ChatEvent } from "./chat-events";
@@ -229,7 +229,7 @@ export const chatMachine = setup({
         messages.push({
           content: event.text,
           isFromAI: true,
-          date: formatDate(),
+          date: todayString(),
         });
       } else {
         const last = messages[messages.length - 1];
@@ -255,7 +255,7 @@ export const chatMachine = setup({
         {
           content: "Something went wrong. Try sending again?",
           isFromAI: true,
-          date: formatDate(),
+          date: todayString(),
         },
       ];
       return { messages, isReplyingAI: false };