Proof of concept fudge scaling to resolve coincident edges
hard coded 1.1 scaling is much too high; actual value can be very wee - just needs to be enough to ensure any corner cases overlap rather than coincide on a shared edge. This permits the CSG operations on the whole model to proceed.

With fudge scaling applied, floor and walls should be adjusted to fit.
Make inflation amount configurable.
translate/scale/translate transformation is always applied, even if inflation == 1, in which case it is unnecessary.