We need this for debugging, as we need some better way to display what
intersects what at what moment. Otherwise it takes a lot of effort to
figure out what is going on.
I had to create some type annotations that appear superfluous. Might be
interference from the `contracts` library. This should be investigated.
I've temporarily removed collision/infringement detection in
`.move_dot()` because it was a lot of effort to get it right. We'll deal
with this later.
There's a panic due to mesh edges not being generated properly from
loose bends. But this commit is already very large, so I'm going to fix
this in the next one.
There's also some nomenclature changes.
`Dot` becomes `FixedDot` and `LooseDot`.
`Seg` becomes `FixedSeg`, `HalfLooseSeg`, and `FullyLooseSeg`.
`Bend` becomes `FixedBend` and `LooseBend`.
The fixed variants differ from the loose variants by being unchangeable
for the router (though probably will be pushable in some cases, but
that's for later). So typically tey're going to be the initial
conditions.
For now only the fixed variants are used even if actually loose, to
split this change into several commits.