2D elements: plane stress, plane strain and axisymmetric sections on the DOF framework; mesh.planar (M4) (#39)

Model: planar section kinds with Extent, element edges in sets, edge-weighted 2D loads,
centrifugal load, 2D model checks. fem: Plane kernels on Basis::{Tri3,Tri6,Quad4,Quad8}
declaring ElementDofs::new(DofSet::PLANE); QM6 incompatible modes with the
Wilson-Ibrahimbegovic correction. Solver: Kernel enum on the DofLayout; 3D results
bit-identical (hash-checked). Decks: Abaqus CPS/CPE/CAX, Nastran membranes and RFORCE,
LS-DYNA ELFORM 12/13. Mesh: free triangle mesher, planar region meshing, face boundaries.
Engine: mesh.planar with tagged edges. Analytic verification suite in solver/tests/plane.rs.


Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/catalogue.rs

@@ -168,6 +168,13 @@ pub static CATALOGUE: &[Capability] = &[
     ),
     soon("mesh.order.quadratic", "Quadratic", Mesh, "Tet", "M2", "Second-order elements with mid-side nodes on the geometry"),
     ready("mesh.delaunay.points", "Delaunay Points", Mesh, "Tet", "Delaunay tetrahedralization of a point list (debugging aid)"),
+    ready(
+        "mesh.planar",
+        "2D Mesh",
+        Mesh,
+        "2D",
+        "Quad or triangle mesh of a planar face or polygon in the XY plane for plane stress, plane strain and axisymmetric models; edges tagged",
+    ),
     soon("mesh.quad.faces", "Quad Faces", Mesh, "Structured Hex", "M5", "All-quad meshes of faces on shared edge nodes"),
     soon("mesh.hex.mapped", "Mapped Hex", Mesh, "Structured Hex", "M5", "Mapped hex mesh of six-sided regions"),
     soon("mesh.hex.sweep", "Sweep Hex", Mesh, "Structured Hex", "M5", "Hex mesh swept along extrusions and revolutions"),
@@ -213,7 +220,7 @@ pub static CATALOGUE: &[Capability] = &[
         "Section",
         Properties,
         "Sections",
-        "Solid, shell, beam or rod section assigned to a set, with its element formulation",
+        "Solid, shell, beam, rod or 2D (plane stress, plane strain, axisymmetric) section assigned to a set, with its element formulation",
         &["model.section.edit", "model.section.delete"],
     ),
     soon("model.section.composite", "Composite", Properties, "Sections", "M8", "Composite layups and continuum shells"),