build doesn't preserve the box's shrunken state

[rigdern]

Repro steps

I reproed this with Boxer 3.4.19 2024-06-24

1. Download, unzip, and open build doesn't maintain box's shrunken state repro.box.zip
2. Run get-shrunk-date-and-time

Expected result: The returned time-box is shrunken just as it was in the call to build.

Actual result: The returned time-box is expanded.

Here's a screenshot of the full repro box:

Use case

This capability could be useful if you want to return a box that you'll know will have a large amount of content.