Animaton: Drop into collapsed thought

[raineorshine]

Steps to Reproduce

- a
- b
- c
- d
- e

Drag and drop a into d.

Current Behavior

a disappears and the rest of the thoughts translate into place:

Drop.into.collapsed.thought.mov

Expected Behavior

a should translate to the destination thought and then disappear.

This should only occur if the destination is collapsed and thus the dragged thought is unmounted. If the destination thought is expanded (or will be expanded after the drop, such as when the cursor is on the dragged thought), then it should translate into place as normal (current behavior).