Edge case in v3.0.0 worked correctly in v2.5.1

[docEdub]

I have an edge case in Babylon.js that worked correctly in manifold-3d v2.5.1 but adds extra edges when switching to manifold-3d v3.0.0.

I've repro'd the issue in a Babylon.js playground:
https://playground.babylonjs.com/?manifold=3#1DWRFP#3

Using the older version of manifold-3d shows the expected result:
https://playground.babylonjs.com/?manifold=2#1DWRFP#3

Apologies for not using the manifold-3d playground, but I did not see a way to show edges and normals there. I exposed the manifold-3d types towards the end of the Babylon playground at line 63, and logged out the result mesh vertProperties as an example if it helps.

I tried comparing the resulting vertices from each version, but the diff is too varied to show the issue immediately, so I'm hoping some expert eyes will take a look.

[elalish]

Is the resulting object incorrect? We don't guarantee that e.g. the number of verts, edges, etc are consistent from version to version, as there are many correct answers. Does the volume or surface area change in a noticeable way? That's a better way to test regression.