iter(g31): 新增 tree 树形组件

packages/skin/ui/ua.manifest.json

@@ -54,7 +54,8 @@
       "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",
@@ -1732,6 +1733,48 @@
           "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）"
+        ]
       }
     ]
   }