Explicit X2: large deformation, J2 and Johnson-Cook plasticity, damage and erosion (M10)

- model: materials gain solver-neutral plastic (bilinear isotropic/kinematic,
  hardening table, Johnson-Cook with adiabatic heating), damage (Johnson-Cook
  D1-D5) and erosion (plastic strain); explicit steps gain nonlinear_geometry
  (default on) and stress_rate (jaumann | green_naghdi).
- fem: rotation (Hughes-Winget, Flanagan-Taylor), plasticity (radial return,
  capped bracketed Newton for Johnson-Cook, damage; the update takes the
  mechanical strain increment so thermal strains can be subtracted), closed-form
  hex8 gradients for deformed configurations.
- explicit: updated Lagrangian hex8/tet4, per-element material state, erosion
  with reported energy, plastic work in the energy account.
- solver: warns that the linear solver uses the elastic constants of plastic
  materials (results hash-identical).
- decks: Abaqus *PLASTIC (+ Johnson-Cook keywords), Nastran MATS1/TABLES1,
  LS-DYNA *MAT_PLASTIC_KINEMATIC / *MAT_PIECEWISE_LINEAR_PLASTICITY; what a
  format cannot express is reported as Unsupported.
- engine: model.material.plasticity, model.material.damage (catalogue ready),
  explicit element probe, eroded elements in the solve summary.

Step commits before the rebase onto the DOF framework: branch explicit-x2-steps.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

docs/features.md

@@ -5,7 +5,7 @@ Generated from the capability catalogue (`crates/engine/src/catalogue.rs`) by
 Every entry is a toolbar button. **Ready** entries run their command; **coming soon** entries are
 shown greyed with the roadmap milestone that brings them (ROADMAP.md).
 
-46 ready, 55 coming soon.
+48 ready, 53 coming soon.
 
 ## Geometry
 
@@ -56,9 +56,9 @@ shown greyed with the roadmap milestone that brings them (ROADMAP.md).
 | Panel | Capability | Status | Command |
 |---|---|---|---|
 | Materials | Material — Elastic (isotropic, orthotropic) material with density | ready | `model.material.create`, `model.material.edit`, `model.material.delete` |
-| Materials | Plasticity — Plastic hardening data | coming soon (M8) |  |
+| Materials | Plasticity — Von Mises plasticity: bilinear, hardening table or Johnson–Cook | ready | `model.material.plasticity` |
 | Materials | Hyperelastic — Hyperelastic material models | coming soon (M8) |  |
-| Materials | Damage — Damage initiation and evolution | coming soon (M8) |  |
+| Materials | Damage — Johnson–Cook damage and element erosion | ready | `model.material.damage` |
 | Materials | Thermal — Conductivity, specific heat and expansion | coming soon (M8) |  |
 | Materials | Equation of State — Polynomial, ideal gas, Mie–Grüneisen, JWL and tabulated equations of state | coming soon (M11) |  |
 | Sections | Section — Solid, shell, beam, rod or 2D (plane stress, plane strain, axisymmetric) section assigned to a set, with its element formulation | ready | `model.section.create`, `model.section.edit`, `model.section.delete` |