The deepest level to ask for when the caller does not say.
Callers with a body should pass surfaceDetailFloor instead, which measures
where that field stops having anything to add — level 12 to 19 across the
zoo now that the presentational tail carries sub-floor craters, against 10 to
16 for the canonical field alone and 7 to 10 for the three bands before it.
This is the fallback for a caller holding numbers rather than a body, and it
is deliberately no deeper than any of them — it is the shallowest the zoo
measures — so forgetting to pass one is visible as coarse ground rather than
as a budget that will not close. Twelve rather than thirteen because Miranda
is the shallowest and it is twelve; a fallback one level past a body's own
floor is the failure this constant exists to prevent, arriving through the
constant.