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/mesh/src/mirror.rs

@@ -23,6 +23,8 @@ pub fn reflected_order(kind: ElementKind) -> Option<&'static [usize]> {
         ElementKind::Tet10 => &[0, 2, 1, 3, 6, 5, 4, 7, 9, 8],
         // Each triangle's last two corners swap.
         ElementKind::Wedge6 => &[0, 2, 1, 3, 5, 4],
+        // The base's corners in reverse cyclic order; the apex stays.
+        ElementKind::Pyramid5 => &[0, 3, 2, 1, 4],
         // Each quadrilateral's corners in reverse cyclic order from its first.
         ElementKind::Hex8 => &[0, 3, 2, 1, 4, 7, 6, 5],
         ElementKind::Hex20 => &[0, 3, 2, 1, 4, 7, 6, 5, 11, 10, 9, 8, 15, 14, 13, 12, 16, 19, 18, 17],