fem: pyramid5 element (solver, quality, decks, VTK)

A five-node pyramid, the conforming transition between a hexahedron's face
and tetrahedra: Bedrosian's rational shape functions with a collapsed (Duffy)
Gauss rule, a certified Jacobian on the base square with exact volume, a
scaled Jacobian, C3D5 / CPYRAM / LS-DYNA degenerate solid, VTK_PYRAMID and
the binary mesh code 13. A distorted hex8-pyramid5-tet4 transition mesh
passes the patch test and uniaxial tension exactly.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/fem/src/shape.rs

@@ -116,6 +116,13 @@ pub fn wedge6(xi: [f64; 3]) -> Shape {
     s
 }
 
+/// Five-node pyramid: base [−1, 1]² at ζ = 0, apex (0, 0, 1), the rational functions of
+/// [`crate::basis`] (Bedrosian 1992), conforming with tetrahedra on its triangles and with
+/// hexahedra on its base.
+pub fn pyramid5(xi: [f64; 3]) -> Shape {
+    crate::basis::Basis::Pyramid5.eval(xi)
+}
+
 /// Twenty-node serendipity hexahedron.
 pub fn hex20(xi: [f64; 3]) -> Shape {
     let mut s = Shape::new(20);