One solution is to avoid saving the mesh. That is, replace:
# Save the mesh, and read back in as a Ferrite Grid
grid = mktempdir() do dir
path = joinpath(dir, "mesh.msh")
gmsh.write(path)
togrid(path)
end
with simply:
# Skip file I/O and convert GMSH data directly to Ferrite Grid
grid = togrid()