First, from now on I'm going to call the "SDL2 demo" the "SDL2 bench",
as a demo is software that exists to demonstrate, whereas its purpose
lately has been only fast prototyping, as we switched to make all demo
animations in the Egui port anyway.
Second, I'm removing the SDL2 bench anyway as it's a maintenance burden
that lost its utility. It's also affected by a bug in Pathfinder that
makes it impossible to zoom beyond a certain threshold which would
require someone to dig into Pathfinder's codebase, a task I don't think
anyone is interested in.
Disambiguate between node indices and (teir inner) petgraph indices.
Rename "band index" to "band first seg index", as we identify bands by
teir first segs. Rename "trianvertex index" and "navvertex index"
respectively to "trianvertex node index" and "navvertex node index", as
these point to nodes on the geometry graph and only indirectly to
vertices on the vertex graph.