chore(backlog): 记录 g19 完成

.ua/backlog.json

@@ -514,7 +514,7 @@
       "title": "textarea 字数统计",
       "motivation": "多行输入常配字数上限，用户需要 n/limit 实时反馈而不是提交后才报错",
       "acceptance": "maxCount 传入后 textarea 设原生 maxlength 并在下方附加块显示实时计数，与外部写回同步；npm run check 全绿",
-      "status": "open",
+      "status": "done",
       "notes": "自补：既有组件可用性细节"
     }
   ]

.ua/iterations.log

@@ -63,3 +63,4 @@
 {"ts":"2026-10-26T10:58:01+08:00","id":"g16","result":"done","commit":"a036b0a","summary":"image 加载失败自动替换虚线占位块，fallback 可自定义文案，demo 附失效地址示例"}
 {"ts":"2026-10-26T11:00:20+08:00","id":"g17","result":"done","commit":"27d797a","summary":"select 展开后键入字母按前缀环形快跳选项，1s 无输入重置缓冲，既有键盘导航不变"}
 {"ts":"2026-10-26T11:04:02+08:00","id":"g18","result":"done","commit":"44b8697","summary":"textField clearable 开启后有值即显一键清空按钮，点击同步信号与 onInput，空值自动隐藏"}
+{"ts":"2026-10-26T11:06:38+08:00","id":"g19","result":"done","commit":"34abe3f","summary":"textarea maxCount 设原生 maxlength 并在下方附加块显示实时 n/limit 计数"}