Function lower_scalar_elliptic_cartesian 

pub fn lower_scalar_elliptic_cartesian(
    program: &KernelProgram,
) -> Result<ScalarEllipticCartesianModel, Diagnostic>

Lower a validated canonical scalar elliptic Relation on one runtime- dimensional Cartesian box.

The admitted volume form is -div(k grad(u)) - f = 0 with one positive constant coefficient. Exactly one explicit trace or normal-flux Relation is required on every axis side. Source and boundary data lower to the same immutable, dimension-checked spatial-expression contract.

Errors

Returns EQ0703 when the model is ambiguous or outside this precise canonical subset.