The discovery tool presented itself as the place to inspect options before
selecting a child route, and rejected every provider or model outside the
Session's authorized routes, including providers that do not exist. A model
that skipped the no-argument call therefore had no way to learn the correct
ids or that omission was legal, and repeated identical denials.
Say that queries exist to override the child route, that omitting both route
fields inherits the parent route, that a field is omitted rather than sent
empty, and, in each optional route field, that omitting it inherits the
parent value.