feat: 提醒到期 → LLM生成自然提醒语 → 推送

- Gateway ReminderScheduler 到期时调用 ai-core /api/v1/internal/reminder-trigger
- ai-core 用 LLM 生成温柔俏皮的提醒语，通过 messagePusher 推送
- Thinker 新增 TriggerReminderMessage 方法
- 环境变量: AI_CORE_URL (Gateway 已有)

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

backend/ai-core/cmd/main.go

@@ -516,6 +516,60 @@ func main() {
 		w.Write([]byte(`{"status":"ok"}`))
 	})
 
+	// 提醒触发端点：Gateway 调度器在提醒到期时调用，由 LLM 生成自然提醒语推送
+	mux.HandleFunc("/api/v1/internal/reminder-trigger", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			w.WriteHeader(http.StatusMethodNotAllowed)
+			return
+		}
+		if r.Header.Get("X-Internal-Token") != os.Getenv("INTERNAL_SERVICE_TOKEN") {
+			w.WriteHeader(http.StatusUnauthorized)
+			return
+		}
+		var req struct {
+			Title       string `json:"title"`
+			Description string `json:"description"`
+			UserID      string `json:"user_id"`
+			SessionID   string `json:"session_id"`
+		}
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		// Generate a natural reminder via LLM.
+		prompt := fmt.Sprintf(`【系统提醒】现在有一条提醒到时间了：
+标题：%s
+描述：%s
+
+请用昔涟的口吻，用一句话自然地提醒开拓者。语气温柔俏皮，像朋友间的关心。
+只输出提醒语本身，不要加前缀或引号。`, req.Title, req.Description)
+
+		messages := []model.LLMMessage{
+			{Role: model.RoleSystem, Content: "你是昔涟。用温柔俏皮的语气，一句话提醒开拓者。"},
+			{Role: model.RoleUser, Content: prompt},
+		}
+		ctx, cancel := context.WithTimeout(r.Context(), 15*time.Second)
+		defer cancel()
+		resp, err := chatAdapter.Chat(ctx, messages)
+		if err != nil {
+			log.Printf("[reminder-trigger] LLM生成失败: %v", err)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		reminderMsg := strings.TrimSpace(resp.Content)
+		if reminderMsg == "" {
+			reminderMsg = fmt.Sprintf("开拓者～「%s」的提醒到时间啦♪", req.Title)
+		}
+		log.Printf("[reminder-trigger] 生成提醒语: %s", reminderMsg)
+
+		// Push through the message pusher if available.
+		if thinker != nil {
+			thinker.TriggerReminderMessage(req.UserID, req.SessionID, reminderMsg)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.Write([]byte(`{"status":"ok"}`))
+	})
+
 	mux.HandleFunc("/api/v1/health", func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
 		w.Write([]byte(`{"status":"ok","service":"ai-core","model":"` + chatAdapter.ModelName() + `"}`))

backend/ai-core/internal/background/thinker.go

@@ -350,6 +350,26 @@ func (t *Thinker) UpdatePresence(online bool, sessionID string) {
 	}
 }
 
+// TriggerReminderMessage pushes a reminder message generated by LLM to the user.
+// Called by the internal reminder-trigger endpoint when a reminder fires.
+func (t *Thinker) TriggerReminderMessage(userID, sessionID, message string) {
+	t.mu.Lock()
+	pusher := t.messagePusher
+	pushSessionID := sessionID
+	if pushSessionID == "" {
+		pushSessionID = t.activeSessionID
+	}
+	if pushSessionID == "" {
+		pushSessionID = t.adminSessionID
+	}
+	t.mu.Unlock()
+
+	if pusher != nil && message != "" {
+		log.Printf("[提醒推送] 推送LLM提醒: user=%s session=%s msg=%s", userID, pushSessionID, message)
+		pusher(userID, pushSessionID, message)
+	}
+}
+
 // ThinkerConfig 后台思考配置
 type ThinkerConfig struct {
 	Enabled          bool