feat(chat): handle credit-gated send responses

src/data/schemas/chat/chat_send_response.ts

@@ -3,17 +3,24 @@
  * 
  */
 import { z } from "zod";
+import { booleanOrFalse, stringOrNull } from "../nullable-defaults";
 import { ChatImageSchema, ChatLockDetailSchema } from "./chat_payloads";
 
 export const ChatSendResponseSchema = z.object({
   reply: z.string(),
   audioUrl: z.string().default(""),
   messageId: z.string(),
-  isGuest: z.boolean().default(false),
+  isGuest: booleanOrFalse,
   // 函数式 default —— 每次 parse 时重新调 Date.now()（后端不返回 timestamp 时用当下时间）
   timestamp: z.number().default(() => Date.now()),
   image: ChatImageSchema,
   lockDetail: ChatLockDetailSchema,
+  canSendMessage: z.boolean().default(true),
+  cannotSendReason: stringOrNull,
+  creditBalance: z.number().default(0),
+  creditsCharged: z.number().default(0),
+  requiredCredits: z.number().default(0),
+  shortfallCredits: z.number().default(0),
 });
 
 export type ChatSendResponseInput = z.input<typeof ChatSendResponseSchema>;