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/conformal_mesh.hpp

@@ -41,30 +41,42 @@ namespace conformallab {
 // ── Kernel ──────────────────────────────────────────────────────────────────
 // Simple double-precision Cartesian.  Conformal mapping algorithms never
 // need exact arithmetic — they operate on floating-point lengths and angles.
+
+/// CGAL kernel used by all conformallab algorithms (double precision).
 using Kernel = CGAL::Simple_cartesian<double>;
+/// 3-D point type (vertex coordinates).
 using Point3 = Kernel::Point_3;
+/// 2-D point type (UV-domain layout coordinates).
 using Point2 = Kernel::Point_2;
 
 // ── Mesh type ────────────────────────────────────────────────────────────────
+/// Triangle mesh carrying all conformal-map data as property maps.
 using ConformalMesh = CGAL::Surface_mesh<Point3>;
 
 // ── Index/descriptor aliases (CGAL 6.x naming) ───────────────────────────────
+/// Vertex descriptor of `ConformalMesh`.
 using Vertex_index   = ConformalMesh::Vertex_index;
+/// Half-edge descriptor of `ConformalMesh`.
 using Halfedge_index = ConformalMesh::Halfedge_index;
+/// Edge descriptor of `ConformalMesh`.
 using Edge_index     = ConformalMesh::Edge_index;
+/// Face descriptor of `ConformalMesh`.
 using Face_index     = ConformalMesh::Face_index;
 
 // ── Geometry type constant (replaces Java CoFace.type enum) ─────────────────
+/// Discrete geometry type that a face/mesh is interpreted in.
+/// Replaces the original Java `CoFace.type` enum.
 enum class GeometryType : int {
-    Euclidean  = 0,
-    Hyperbolic = 1,
-    Spherical  = 2
+    Euclidean  = 0, ///< Flat metric (ℝ²).
+    Hyperbolic = 1, ///< Hyperbolic metric (ℍ²).
+    Spherical  = 2  ///< Spherical metric (S²).
 };
 
 // ── Standard property-map bundles ────────────────────────────────────────────
 
-// Add the vertex properties used by all conformal-map functionals.
-// Returns {lambda, theta, idx}.
+/// Register and return the vertex-side property maps used by all five
+/// DCE functionals: `v:lambda` (log conformal factor), `v:theta` (target
+/// cone angle), `v:idx` (contiguous integer index).
 inline auto add_vertex_properties(ConformalMesh& mesh)
 {
     auto [lambda, ok1] = mesh.add_property_map<Vertex_index, double>("v:lambda", 0.0);
@@ -74,7 +86,8 @@ inline auto add_vertex_properties(ConformalMesh& mesh)
     return std::make_tuple(lambda, theta, idx);
 }
 
-// Add the edge intersection-angle property used by the hyperbolic functional.
+/// Register and return the edge intersection-angle property `e:alpha`
+/// (used by the hyper-ideal functional).
 inline auto add_edge_properties(ConformalMesh& mesh)
 {
     auto [alpha, ok] = mesh.add_property_map<Edge_index, double>("e:alpha", 0.0);
@@ -82,7 +95,7 @@ inline auto add_edge_properties(ConformalMesh& mesh)
     return alpha;
 }
 
-// Add the face geometry-type property.
+/// Register and return the per-face geometry-type property `f:type`.
 inline auto add_face_properties(ConformalMesh& mesh)
 {
     auto [ftype, ok] = mesh.add_property_map<Face_index, int>(