chore(backlog): 记录 g91 完成

.ua/backlog.json

@@ -1091,7 +1091,7 @@
       "motivation": "formItem 只有 label 与错误位，没有「格式提示」的位置：调用方只能把说明塞进 placeholder 或标签里，一报错提示就被替换得无处可看，用户不知道正确格式是什么",
       "acceptance": "FormItemProps 新增可选 hint，渲染在控件下方；校验失败时 hint 让位（hidden）只留错误文案，校验通过自动恢复；样式走令牌；文档参数表（formItem 前缀）与演示同步；npm run check 全绿",
       "notes": "自补：表单可用性；不改 formItem 返回句柄与 form 聚合逻辑",
-      "status": "open"
+      "status": "done"
     }
   ]
 }

.ua/iterations.log

@@ -135,3 +135,4 @@
 {"ts":"2026-10-26T13:08:26+08:00","id":"g88","result":"done","commit":"9a7c46a","summary":"内核 getAllRows 跳过分页取全量派生行，表格 exportable 导出 CSV（BOM+转义），冒烟补 4 条"}
 {"ts":"2026-10-26T13:09:11+08:00","id":"g89","result":"done","commit":"68ca2ba","summary":"esbuild 开 minifyWhitespace/minifySyntax，demo.html 278KB→205KB，标识符保留"}
 {"ts":"2026-10-26T13:09:49+08:00","id":"g90","result":"done","commit":"1e6898b","summary":"重新生成 CHANGELOG（253 提交），changelog:check 恢复一致"}
+{"ts":"2026-10-26T13:10:40+08:00","id":"g91","result":"done","commit":"47756c8","summary":"formItem 新增 hint 辅助说明，报错时自动让位给错误文案"}