model: nonlinear static steps and neo-Hookean hyperelasticity, mapped by the deck writers

A nonlinear_static procedure (nonlinear geometry, initial/min/max increments,
increment and iteration caps, force/displacement/energy tolerances, line
search), validated with caps against hostile values. Materials gain an
explicit hyperelastic option (decoupled compressible neo-Hookean on the
isotropic constants). Abaqus writes *STEP, NLGEOM, INC / *STATIC with the
increments and *HYPERELASTIC, NEO HOOKE; LS-DYNA writes the ramped implicit
run with full Newton and *CONTROL_IMPLICIT_AUTO; Nastran refuses SOL 400 by
name, as LS-DYNA does hyperelastic materials in nonlinear steps. Explicit
dynamics refuses hyperelastic materials by name; solve.run names the solver
still to come.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

crates/model/src/check.rs

@@ -322,6 +322,7 @@ impl Model {
                     Procedure::ExplicitDynamic(_) => "is dynamic",
                     Procedure::HeatTransfer { transient: Some(_) } => "is transient heat transfer",
                     Procedure::Static {}
+                    | Procedure::NonlinearStatic(_)
                     | Procedure::Fluid { .. }
                     | Procedure::HeatTransfer { transient: None }
                     | Procedure::CoupledTemperatureDisplacement {} => {
@@ -469,7 +470,7 @@ impl Model {
                 }
             }
             match &s.procedure {
-                Procedure::Static {} => {
+                Procedure::Static {} | Procedure::NonlinearStatic(_) => {
                     if s.loads.is_empty() && !prescribes_motion {
                         d.warning(&subject, "nothing loads the model in this step");
                     }