Stable position when reordering sidebar sections

[markjaquith]

When you drag sidebar sections, they collapse, which is nice. But they also shoot up to the top, so your cursor is often hundreds of pixels away from the thing you're dragging, which feels wrong.

MOV_0421.mp4

How do we feel about making the dragged item stable, and collapsing the other sections around that stable drag point?

MOV_8524.mp4