EphemerisSamplingError and ManeuverApplicationError were missing the
attribute the other fifteen error kinds carry. Record the distinction
between an error enum, which is marked so a new category does not break a
caller, and a domain state enum, which is left exhaustive so the compiler
points at every match that a new variant needs.
Thirty four crates listed apsis-core or apsis-math without referencing it,
and apsis-kepler listed apsis-time and apsis-tle as well. Each was verified
removable by compiling with it taken out. An unused dependency still costs
build time and makes the dependency graph and the layer check report
relations that do not exist. The layer check now reports 104 edges, down
from 141.