fix: 修复 mp-weixin 模板箭头函数和 TextDecoder 不兼容

- 微信小程序 wxml 模板不支持内联箭头函数
  @submit 改为方法引用，submitClarification 自己找未提交卡片
- TextDecoder 在 mp-weixin 不可用
  decodeChunk 改用纯 JS UTF-8 解码实现

mini-program/src/services/shortNovel.js

@@ -106,11 +106,36 @@ export const followupStream = ({ sessionId, action, payload, onEvent, onError })
 
 /**
  * 解码 chunk 数据
+ * 兼容 mp-weixin（不支持 TextDecoder）
  */
 function decodeChunk(chunk) {
   if (typeof chunk === 'string') return chunk
-  const decoder = new TextDecoder('utf-8')
-  return decoder.decode(new Uint8Array(chunk))
+  // 小程序环境 chunk 可能是 ArrayBuffer，转成 UTF-8 字符串
+  const bytes = new Uint8Array(chunk)
+  let result = ''
+  let i = 0
+  while (i < bytes.length) {
+    const byte1 = bytes[i++]
+    if (byte1 < 0x80) {
+      result += String.fromCharCode(byte1)
+    } else if (byte1 < 0xE0) {
+      const byte2 = bytes[i++]
+      result += String.fromCharCode(((byte1 & 0x1F) << 6) | (byte2 & 0x3F))
+    } else if (byte1 < 0xF0) {
+      const byte2 = bytes[i++]
+      const byte3 = bytes[i++]
+      result += String.fromCharCode(((byte1 & 0x0F) << 12) | ((byte2 & 0x3F) << 6) | (byte3 & 0x3F))
+    } else {
+      const byte2 = bytes[i++]
+      const byte3 = bytes[i++]
+      const byte4 = bytes[i++]
+      const codePoint = ((byte1 & 0x07) << 18) | ((byte2 & 0x3F) << 12) | ((byte3 & 0x3F) << 6) | (byte4 & 0x3F)
+      // 转成 UTF-16 代理对
+      const adjusted = codePoint - 0x10000
+      result += String.fromCharCode(0xD800 | (adjusted >> 10)) + String.fromCharCode(0xDC00 | (adjusted & 0x3FF))
+    }
+  }
+  return result
 }
 
 /**