Function lower_steady_incompressible_stokes_cartesian_2d 

pub fn lower_steady_incompressible_stokes_cartesian_2d(
    program: &KernelProgram,
) -> Result<SteadyIncompressibleStokesCartesianModel2d, Diagnostic>

Lower the exact canonical 2D steady incompressible Stokes subset.

Recognition is identity-parametric and whole-model fail-closed. Source names, package provenance, and declaration order are not part of the contract.

Errors

Returns EQ0703 when the admitted Model is ambiguous, incomplete, or contains meaning outside this deliberately narrow subset.