docs: meshing literature survey and the tet/hex pipeline it chooses (#1)

Survey of about 75 papers on robust predicates, Delaunay tetrahedralization, boundary
recovery, quality improvement and hexahedral meshing, with verified DOIs and the
licence of every associated code base. Architecture and roadmap now name the chosen
methods (robust CDT after Diazzi et al. 2023; octree-dual all-hex first). ADR 0001
adds the licence findings and the test-geometry rule.


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

Co-authored-by: jyviko <[email protected]>
Co-authored-by: Claude Opus 5.5 <[email protected]>

ROADMAP.md

@@ -7,8 +7,8 @@ LS-PrePost, with hexahedral meshing as the centre of gravity, plus its own linea
 |---|---|---|
 | M0 Foundation | Workspace, quality gates (`cargo xtask ci`), FE model, command engine with rollback and panic guard, CLI, geometry boundary on SolidCraft's kernel and tessellator | done |
 | M1 Surface preparation | Robust adaptive-precision predicates; weld, closed/manifold/orientation checks and feature edges on the tessellated boundary; mesh quality metrics | next |
-| M2 Tetrahedral meshing | 3D Delaunay (Bowyer–Watson), boundary recovery, Delaunay refinement to a size field, Voronoi-based optimization (CVT/ODT), sliver removal; linear and quadratic tets | planned |
-| M3 Hexahedral meshing (core) | Method from the literature survey: a hex mesher whose output is always valid, then quality-driven methods; hex-dominant fallback | planned |
+| M2 Tetrahedral meshing | Bowyer–Watson Delaunay, robust constrained Delaunay boundary recovery (Diazzi et al. 2023), Delaunay refinement to a size field, ODT smoothing, Klingner–Shewchuk sliver removal; linear and quadratic tets | planned |
+| M3 Hexahedral meshing (core) | Octree/grid dual all-hex (valid on any input), then hex-dominant by tet recombination, then polycube for blocky parts; see docs/meshing/literature.md | planned |
 | M4 Model definition | Materials, sections, sets and surfaces, boundary conditions, loads, steps, output requests | planned |
 | M5 Solver decks | Abaqus input, Nastran bulk data, LS-DYNA keyword: writers first, then readers | planned |
 | M6 Linear solver | Element library, sparse assembly, linear static and modal analysis, verified against analytic solutions | planned |