docs(doxygen): fix critical extraction bug; baseline 24% → 42% on public API

ROOT CAUSE FIX
The Doxyfile EXCLUDE_PATTERNS line contained `*/* 2.hpp` (note the
space — a stray glob from macOS-style "foo 2.hpp" duplicate files).
That pattern was silently matching ALL .hpp / .h files, so Doxygen was
indexing nothing under code/include/.  The pre-existing 556 KB of HTML
output was effectively documenting only README.md, CLAUDE.md and a
small stub for std:: — not the C++ API at all.

After fixing the pattern (and properly escaping the space-prefixed
"foo 2.hpp / foo 2.h" macOS-dup patterns), Doxygen now extracts 141
compounds and emits 248 HTML pages from the public headers.

WHAT THIS PR ADDS
1. Doxyfile fix: correct EXCLUDE_PATTERNS; add GENERATE_XML for the
   coverage measurement script; add MathJax for `$$...$$` math in
   markdown; add the missing CGAL `\cgalParamNBegin/End/Description/
   Default/...` aliases so CGAL-style param blocks render correctly.

2. New headers:
   - code/include/CGAL/Conformal_map/doxygen_groups.h
     defines `PkgConformalMap{,Ref,Concepts,NamedParameters}`,
     resolving 17 prior "non-existing group" warnings.
   - code/include/CGAL/Conformal_map/doxygen_namespaces.h
     gives every namespace under `CGAL::` and `conformallab::` a
     brief description.

3. New tool: scripts/doxygen-coverage.sh
   Parses the XML output and reports % of public symbols (excluding
   the `detail::` implementation namespaces by default) that have a
   non-empty brief/detailed description.  Supports `--list-undoc`
   and `--threshold N` for CI integration.

4. Substantial docstring additions to the public CGAL headers:
   `Conformal_map_traits.h`, `Discrete_circle_packing.h`,
   `Discrete_inversive_distance.h`, `conformal_mesh.hpp`,
   `Discrete_conformal_map.h` (Hyper_ideal_map_result fields).

5. Markdown housekeeping that the strict-warning Doxygen run surfaced:
   tests.md (escape literal `#` in table cell),
   locked-vs-flexible.md (broken section anchor),
   overall_pipeline.md (replace `$$LaTeX$$` with inline-unicode math).

CURRENT NUMBERS

  before:  ~24%  documented (public API; the prior "87%" claim was
                 based on the broken extraction)
  after:    42%  documented   (165 of 396 public symbols)
  warnings: 0   (was 27 spurious + a flood of bogus undocumented
                  warnings hidden by the buggy EXCLUDE pattern)

NEXT (in a follow-up commit on this branch)
The remaining 231 public symbols (mostly in `layout.hpp`,
`hyper_ideal_functional.hpp`, `spherical_functional.hpp`, the per-mode
functional/Hessian files) can be brought to ~100% with another pass of
short `///` brief descriptions.  The coverage script is the gate; CI
can begin enforcing `--threshold 95` once the next pass lands.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

code/include/CGAL/Discrete_circle_packing.h

@@ -38,26 +38,51 @@ namespace CGAL {
 
 // ── Default traits for CP-Euclidean ───────────────────────────────────────────
 
+/*!
+\ingroup PkgConformalMapConcepts
+\brief Traits class for `discrete_circle_packing_euclidean()` —
+declares the kernel, mesh and property-map types used by the
+BPS-2010 face-based circle-packing functional.
+
+Primary template; specialise it for non-`Surface_mesh` triangle meshes.
+*/
 template <typename TriangleMesh,
           typename Kernel_ = CGAL::Simple_cartesian<double>>
 struct Default_cp_euclidean_traits;
 
+/*!
+\ingroup PkgConformalMapConcepts
+\brief Specialisation for `CGAL::Surface_mesh<P>`; the only one shipped
+in Phase 8b-Lite.
+*/
 template <typename K>
 struct Default_cp_euclidean_traits<CGAL::Surface_mesh<typename K::Point_3>, K>
 {
+    /// CGAL kernel parameter (defaults to `Simple_cartesian<double>`).
     using Kernel        = K;
+    /// Scalar field type used for all CP-Euclidean DOFs (`ρ_f`, `θ_e`, `φ_f`).
     using FT            = typename K::FT;
+    /// 3-D point type (vertex coordinates).
     using Point_3       = typename K::Point_3;
+    /// Triangle-mesh type this specialisation targets.
     using Triangle_mesh = CGAL::Surface_mesh<Point_3>;
 
+    /// Boost-graph vertex descriptor for `Triangle_mesh`.
     using Vertex_descriptor   = typename boost::graph_traits<Triangle_mesh>::vertex_descriptor;
+    /// Boost-graph half-edge descriptor for `Triangle_mesh`.
     using Halfedge_descriptor = typename boost::graph_traits<Triangle_mesh>::halfedge_descriptor;
+    /// Boost-graph edge descriptor for `Triangle_mesh`.
     using Edge_descriptor     = typename boost::graph_traits<Triangle_mesh>::edge_descriptor;
+    /// Boost-graph face descriptor for `Triangle_mesh`.
     using Face_descriptor     = typename boost::graph_traits<Triangle_mesh>::face_descriptor;
 
     // CP-Euclidean property maps — note the *face* DOF index map.
+
+    /// Property map face → contiguous integer DOF index (legacy `cf:idx`).
     using Face_index_pmap = typename Triangle_mesh::template Property_map<Face_descriptor,   int>;
+    /// Property map edge → intersection angle θₑ (legacy `ce:theta`).
     using Theta_e_pmap    = typename Triangle_mesh::template Property_map<Edge_descriptor,   FT>;
+    /// Property map face → target angle sum φ_f (legacy `cf:phi`).
     using Phi_f_pmap      = typename Triangle_mesh::template Property_map<Face_descriptor,   FT>;
 };
 
@@ -75,8 +100,11 @@ struct Circle_packing_result
     /// Face DOFs `ρ_f = log R_f` (length = num_faces(mesh); pinned face = 0).
     std::vector<FT> rho_per_face;
 
+    /// Newton iterations actually performed (≤ `max_iterations`).
     int  iterations    = 0;
+    /// Final infinity-norm of the gradient (Newton stopping criterion).
     FT   gradient_norm = FT(0);
+    /// `true` iff `gradient_norm < gradient_tolerance` at exit.
     bool converged     = false;
 };