Fix dragged row corner styling in Sentinel policies

[linear-code]

In Sentinel policies, dragged rows lose their rounded corners while being dragged. This appears to be a limitation of using the drag-and-drop API directly instead of a third-party library, and there seems to be a workaround to investigate.

CleanShot 2026-04-13 at 11.41.08.mp4

[linear-code]

ENG-2685