Probed the new guard against a partially-broken derivation rather than only the
total-failure case the floors were written for: deleting the transitive step from
`_request_reachable`, so only schemas named directly on a request body resolve.
Both floors stay satisfied and `test_the_derivation_reached_a_real_population`
stays GREEN. What reddens is the planted-member test — its plant is reached
through a nested `$ref` exactly so that it can — and the disposition test, since
the nested rows vanish and report as PHANTOM.
So the floors are the crude backstop against a parse that reached nothing at all,
and the planted-member test is what actually holds the walk honest. Recorded in
the docstring, because a floor described as anti-vacuity reads as coverage it does
not have, and the next reader deciding which of these to keep working should know
which one is load-bearing.
timothy
eff4bdfa22