[2.0.64] Smart Belt Undo Behaviors

[wspikes]

https://www.youtube.com/watch?v=Nmqkh-xbqVo

There are two fairly absurd undo-related behaviors; I'm including both in one video since they're likely related. I'd ask that both be tested in the fix.

The behaviors here are on a single Undo action (Ctrl+Z).

For the first part of the video (0:00 - 0:17), why is it deleting the entire belt? I'm pressing Undo once, so I expect it only to delete the parts added above the middle wood box (I demonstrate the expected area just after using the deconstruction planner).

For the second part (0:18 - end), well... I'll let the video speak for itself. It's confounding.

(Credit for finding the first part goes to Midhrin)