large design should not hide strands on hover

[dave-doty]

Typically when hovering over a strand in select mode, it applies the "shadow" filter:

However, in a large design, strands that are sufficiently far from the origin simply disappear on hover:

There seems to be some "bounding box" outside of which this happens. Here's a strand at the corner of the bounding box:

To reproduce, click on File-->Load example-->Very large origami. Strands outside of about the top-left quarter seem to do this. Delete all the staples, then hover over the whole scaffold strand while zoomed out and you can see 3/4 of it disappear: