Expand description
Spatial-ψ derivative bridge.
Self-contained translation layer between the smooth-side
TermCollectionSpec/TermCollectionDesign world and the lower-level
generic family engine (crate::custom_family). It takes the
resolved spatial length-scale terms and produces the per-axis
CustomFamilyBlockPsiDerivative blocks the engine consumes.
Keeping this here (a higher layer than custom_family) lets the engine
stay ignorant of gam_terms::smooth: family modules call into this
bridge instead of the engine reaching up into smooth.