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 <[email protected]>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

crates/engine/src/cmd/solve.rs

@@ -142,6 +142,7 @@ fn run_all(s: &mut Session, _: &Value) -> Result<Value> {
                 Procedure::Frequency { .. } => run_frequency,
                 Procedure::ExplicitDynamic(_) => run_explicit,
                 Procedure::Fluid { .. } => run_fluid,
+                Procedure::NonlinearStatic(_) => run_nonlinear,
             };
             (st.name.clone(), st.procedure.name(), solve)
         })
@@ -193,6 +194,10 @@ fn run_static(s: &mut Session, p: &Value) -> Result<Value> {
     Ok(summary)
 }
 
+fn run_nonlinear(_: &mut Session, _: &Value) -> Result<Value> {
+    Err(EngineError::Params("not supported yet: nonlinear static steps (the nonlinear solver arrives with solve.nonlinear)".into()))
+}
+
 fn run_heat(s: &mut Session, p: &Value) -> Result<Value> {
     let limits = limits(p)?;
     let step = opt::<String>(p, "step")?;