iter(g31): 新增 tree 树形组件

.ua/backlog.json

@@ -604,6 +604,14 @@
       "acceptance": "check 链为 build → demo → style → typecheck → smoke → index → verify → lint-iterations；verify 校验产物含全部 sec-* 锚点（负向删除锚点即失败）；文档四处链路描述同步；npm run check 全绿",
       "status": "done",
       "notes": "自补：门禁改进；文档四处链路描述同步"
+    },
+    {
+      "id": "g31",
+      "title": "新增 tree 树形组件",
+      "motivation": "文件树/组织架构/权限勾选等场景缺组件，只能手写嵌套 DOM，展开态与键盘可达性都要重造",
+      "acceptance": "tree({ nodes, expanded, selected, defaultExpandAll, onSelect }) 递归渲染 + 箭头展开收起 + 点选 + Enter/→/← 键盘 + 禁用不响应；组件数 40→41 三处计数同步；npm run check 全绿",
+      "status": "open",
+      "notes": "自补：组件补充"
     }
   ]
 }

.ua/index.json

@@ -1,6 +1,6 @@
 {
   "$schema": "ui-arch-registry-index/0.1",
-  "generatedAt": "2026-10-26T03:40:46.247Z",
+  "generatedAt": "2026-10-26T03:41:59.549Z",
   "repoRoot": ".",
   "packages": [
     {
@@ -183,7 +183,8 @@
           "descriptions(props)：描述列表，items(label/value/span) 铺进 column 列网格，bordered 切表格形态，窄屏自动单列",
           "statistic(props)：统计数值，标题 + 大号数字 + 前后缀 + 环比趋势，value 变化时 rAF 滚动过渡（400ms easeOutCubic），减弱动效偏好下直落终值",
           "list(props)：列表，header/footer 外壳 + 条目 avatar/title/description/extra，onItemClick 让条目可点击，items 为空回落空状态",
-          "carousel(props)：轮播，items 横排位移，指示点/箭头/←→ 键切换，autoplay 毫秒自动前进且悬停暂停，index 信号可外部受控"
+          "carousel(props)：轮播，items 横排位移，指示点/箭头/←→ 键切换，autoplay 毫秒自动前进且悬停暂停，index 信号可外部受控",
+          "tree(props)：树形，递归节点 + 箭头展开/收起 + 点选节点，键盘 Enter 选中、→ 展开、← 收起，禁用节点不响应"
         ],
         "keyTypes": [
           "ButtonProps",
@@ -1861,6 +1862,48 @@
               "键盘：聚焦轮播后 ←→ 切换，事件不冒泡避免连带切换外层 tabs/menu",
               "指示点与箭头都可点击，末张下一张环形回到首张"
             ]
+          },
+          {
+            "id": "tree",
+            "title": "树形 Tree",
+            "demo": "sec-tree",
+            "props": [
+              {
+                "n": "nodes",
+                "t": "TreeNode[]",
+                "r": 1,
+                "d": "根节点列表，每项 { key, label, children?, disabled? }"
+              },
+              {
+                "n": "expanded",
+                "t": "Signal<string[]>",
+                "d": "展开的 key 集合；不传则内部维护"
+              },
+              {
+                "n": "selected",
+                "t": "Signal<string>",
+                "d": "选中 key 信号；不传则内部维护"
+              },
+              {
+                "n": "defaultExpandAll",
+                "t": "boolean",
+                "d": "首屏展开全部分支；缺省 false"
+              },
+              {
+                "n": "onSelect",
+                "t": "(node: TreeNode) => void",
+                "k": 1,
+                "d": "选中回调：点击标签或 Enter/空格触发"
+              }
+            ],
+            "example": "const sel = signal(''); tree({ nodes: [{ key: 'src', label: 'src', children: [{ key: 'ui', label: 'ui' }] }], selected: sel, onSelect: (n) => console.log(n.key) })",
+            "steps": [
+              "节点树用 { key, label, children } 描述，key 唯一即可（选中与展开都按 key 记）",
+              "传 selected 信号即可外部受控；不传则组件内部维护选中态",
+              "点箭头只展开/收起，点标签才选中；叶子节点箭头位置留空以对齐",
+              "键盘 Enter/空格 选中、→ 展开、← 收起；disabled 节点点击与键盘都不响应",
+              "defaultExpandAll 首屏展开全部分支（外部已给 expanded 初值时以外部为准）"
+            ]
           }
         ]
       },