R1:aaa08edb1251

When users scroll while dragging items, update item positions immediately

Summary:
Fixes T5979. When you drag a task and scroll using the mouse wheel, we don't move the task under your cursor until you move the mouse.

Instead, listen for `scroll` and move the task.

Test Plan:
- Clicked and dragged a task.
- While holding the task and not moving the cursor, used the mouse wheel to scroll.
- The task followed the cursor (previously, it stayed in position until the mouse was moved again).

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