fix(V0.2): 拖动可靠性重做 —— 把手入口 + 打卡排序接入实际渲染视图

问题定位:
- 打卡页实际渲染的是 MergedView (CheckinPage 路由), 上次改的 HabitView
  是未使用的旧组件, 打包时被 tree-shake, 线上自然无任何效果
- 任务列表长按抬起后一动即脱手: touch-action:pan-y 下手指出现纵向分量,
  WebView/渲染器直接把触摸判给滚动并 pointercancel, touchmove preventDefault
  拦不住已决定的滚动 (看板可用只因该模式下页面无纵向可滚祖先)

修复:
- 新增 ⠿ 拖动把手 (touch-action:none): 浏览器按规范完全不接管该触摸,
  按下立即拖动, CDP 触摸仿真验证: 垂直拖动穿过可滚列表正常落点,
  跨组(每天/每周/每月)正确拒绝; 任务行把手拖动换列, 打卡卡片把手组内排序
- useRowDrag/useHabitDrag 抽出 armListeners, 新增 bindHandle 立即激活路径
- MergedView: 组内排序改按 sortOrder (服务端已返回), 拖动落位乐观更新 +
  POST /checkin/habits/reorder, 失败回滚; 打卡点击加拖动余波保护
- 长按路径保留为补充入口 (不可滚场景仍可用)

src/components/task/useRowDrag.js

@@ -59,7 +59,31 @@ export default function useRowDrag({ columns, onDrop }) {
     cleanup()
   }
 
-  /** 绑定到列表行: 行元素需设置 touch-action: pan-y */
+  // 指针监听装配 (capture + 非 passive touchmove: 激活后尽力拦截滚动接管)
+  const armListeners = (ev) => {
+    try { ev.currentTarget.setPointerCapture(ev.pointerId) } catch { /* ignore */ }
+    const el = ev.currentTarget
+    const move = (e2) => onMove(e2)
+    const tm = (e2) => { if (st.current.active) e2.preventDefault() }
+    const up = () => { onUp(); detach() }
+    const cancel = () => {
+      if (st.current.active) lastEnd.current = Date.now()
+      cleanup()
+      detach()
+    }
+    const detach = () => {
+      el.removeEventListener('pointermove', move)
+      el.removeEventListener('pointerup', up)
+      el.removeEventListener('pointercancel', cancel)
+      el.removeEventListener('touchmove', tm)
+    }
+    el.addEventListener('pointermove', move)
+    el.addEventListener('pointerup', up)
+    el.addEventListener('pointercancel', cancel)
+    el.addEventListener('touchmove', tm, { passive: false })
+  }
+
+  /** 绑定到列表行: 行元素需设置 touch-action: pan-y (长按路径, 可滚场景不可靠) */
   const bind = useCallback((task) => ({
     onPointerDown: (ev) => {
       if (ev.button !== undefined && ev.button !== 0) return
@@ -71,34 +95,31 @@ export default function useRowDrag({ columns, onDrop }) {
         if (navigator.vibrate) navigator.vibrate(15)
         setDrag({ task, fromIdx, toIdx: fromIdx })
       }, 400)
-      try { ev.currentTarget.setPointerCapture(ev.pointerId) } catch { /* ignore */ }
-      const el = ev.currentTarget
-      const move = (e2) => onMove(e2)
-      // 激活后拦截触摸滚动: pan-y 下纵向分量稍大浏览器即接管手势并派发
-      // pointercancel (列表是整页长滚动容器, 必现), 非 passive touchmove
-      // preventDefault 才能真正拦住, 拖动期间指针事件得以持续派发
-      const tm = (e2) => { if (st.current.active) e2.preventDefault() }
-      const up = () => { onUp(); detach() }
-      const cancel = () => {
-        if (st.current.active) lastEnd.current = Date.now()
-        cleanup()
-        detach()
-      }
-      const detach = () => {
-        el.removeEventListener('pointermove', move)
-        el.removeEventListener('pointerup', up)
-        el.removeEventListener('pointercancel', cancel)
-        el.removeEventListener('touchmove', tm)
-      }
-      el.addEventListener('pointermove', move)
-      el.addEventListener('pointerup', up)
-      el.addEventListener('pointercancel', cancel)
-      el.addEventListener('touchmove', tm, { passive: false })
+      armListeners(ev)
     },
     // 长按不弹系统菜单 (配合 CSS user-select:none, 防长按变文字选择)
     onContextMenu: (ev) => ev.preventDefault(),
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }), [ordered, onDrop])
 
-  return { drag, bind, cancel: cleanup, justEnded }
+  /** 绑定到行尾拖动把手: 把手需 touch-action: none, 按下立即拖动。
+   *  pan-y 下整页可滚时浏览器滚动接管会取消指针流 (Android WebView 必现),
+   *  把手路径浏览器完全不接管, 是可靠入口。 */
+  const bindHandle = useCallback((task) => ({
+    onPointerDown: (ev) => {
+      if (ev.button !== undefined && ev.button !== 0) return
+      const fromIdx = ordered.findIndex((c) => c.id === task.columnId)
+      if (fromIdx < 0) return
+      ev.stopPropagation() // 不触发行自身的长按路径
+      st.current = { ...st.current, startX: ev.clientX, startY: ev.clientY, task, fromIdx, toIdx: fromIdx, active: false }
+      st.current.active = true
+      if (navigator.vibrate) navigator.vibrate(15)
+      setDrag({ task, fromIdx, toIdx: fromIdx })
+      armListeners(ev)
+    },
+    onContextMenu: (ev) => ev.preventDefault(),
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }), [ordered, onDrop])
+
+  return { drag, bind, bindHandle, cancel: cleanup, justEnded }
 }