fix: 返回按钮用 TouchDelegate 扩大点击区域

图标大小不变，触摸区域向下扩展 20dp、向右扩展 10dp
解决用户点偏到下方内容区的问题

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/main/java/com/xiaoqu/watch/ui/task/TaskListFragment.kt

@@ -87,10 +87,19 @@ class TaskListFragment : BaseFragment<FragmentTaskListBinding>() {
         val dialogContainer = requireActivity().findViewById<FrameLayout>(R.id.dialog_container)
         tipDialog = QuTipDialog(dialogContainer)
 
-        // 返回按钮
+        // 返回按钮（扩大触摸区域，图标大小不变）
         binding.btnBack.setOnClickListener {
             findNavController().popBackStack()
         }
+        // 用 TouchDelegate 向下和向右扩展点击区域
+        binding.btnBack.post {
+            val parent = binding.btnBack.parent as View
+            val rect = android.graphics.Rect()
+            binding.btnBack.getHitRect(rect)
+            rect.bottom += (20 * resources.displayMetrics.density).toInt()
+            rect.right += (10 * resources.displayMetrics.density).toInt()
+            parent.touchDelegate = android.view.TouchDelegate(rect, binding.btnBack)
+        }
 
         // 左右滑手势（切换任务），上下滑留给内容滚动
         gestureDetector = GestureDetector(requireContext(), object : GestureDetector.SimpleOnGestureListener() {