chore(backlog): 记录 g81 完成

.ua/backlog.json

@@ -1011,7 +1011,7 @@
       "motivation": "每行都写死 tabindex=0，键盘用户从树里穿过去要按 N 次 Tab（20 个节点就是 20 次），违反 WAI-ARIA 树模式「整棵树一个 Tab 停点、行间用方向键」的要求",
       "acceptance": "只有当前行 tabindex=0 其余 -1；焦点落到哪行停点就跟到哪行（focusin 同步），下次 Tab 直接回到该行；↑↓/Home/End 移动后停点随焦点迁移；初始停点为首个未禁用根节点；tree ≤ 200 行；npm run check 全绿",
       "notes": "自补：无障碍；keyOf 抽出复用，去掉 keydown 里的内联查找",
-      "status": "open"
+      "status": "done"
     }
   ]
 }

.ua/iterations.log

@@ -125,3 +125,4 @@
 {"ts":"2026-10-26T12:56:05+08:00","id":"g78","result":"done","commit":"b9261fb","summary":"新增 space 间距容器：flex gap 托管子元素间距，size 走令牌或像素，direction/align/justify/wrap/block 可调，清单与演示同步"}
 {"ts":"2026-10-26T12:57:15+08:00","id":"g79","result":"done","commit":"2c0b9fd","summary":"可排序表头进 Tab 序，Enter/空格 与点击共用同一 toggle，补 scope=col"}
 {"ts":"2026-10-26T12:58:08+08:00","id":"g80","result":"done","commit":"c324afc","summary":"通知自动关闭改为可暂停：悬停/聚焦扣减已流逝时间，离开按剩余续计"}
+{"ts":"2026-10-26T12:58:56+08:00","id":"g81","result":"done","commit":"f3c83e9","summary":"树改 roving tabindex：整棵树一个 Tab 停点，focusin 跟随焦点，keydown 复用 keyOf"}