fix: correct 16 inconsistencies found by consistency audit

Math / code:
- layout.hpp: add explanatory comment for Möbius deck transformation
  (from_three with z1=w1, z2=w2 encodes T fixing cut-edge endpoints)
- layout.hpp: document spherical holonomy limitation — Vector2d stores
  only (x,y) of 3-D position diff; full SO(3) representation deferred

Gradient sign convention (CLAUDE.md was wrong):
- Euclidean and Spherical both use G_v = Θ_v − actual (target minus actual)
- HyperIdeal uses G_v = actual − Θ_v
- Hessian sign differs: Euclidean PSD, Spherical NSD → −H, HyperIdeal PSD

Test counts (were inconsistent across all files):
- Actual: 176 CGAL tests, 2 GTEST_SKIP (not 173/170/174, not 1 skip)
- The 2 skips are EuclideanFunctional + SphericalFunctional Hessian gradient
  checks (Java @Ignore ports) — not HyperIdeal Hessian as previously stated
- doc/api/tests.md: add missing SmokeEuclidean suite (3 tests),
  EuclideanLayout (2), SphericalLayout (1), fix GaussBonnet 8→12,
  MeshIO 9→6, Layout 8→6, EuclideanFunctional 11→12,
  HomologyGenerators no longer a GTEST_SKIP stub (live test on brezel2.obj)
- doc/roadmap/phases.md: Phase 7 cumulative 158→176 tests
- doc/roadmap/phases.md: Phase 3 clarified — HyperIdeal Hessian is FD
- CLAUDE.md: suite count 28→34, test ref 173+36→174+36
- scripts/try_it.sh: expected output 173/1 skipped → 174/2 skipped

CI table (CLAUDE.md):
- test-cgal now triggers on pull requests only (not main/dev pushes)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

doc/roadmap/phases.md

@@ -16,7 +16,9 @@
 Phase 1   Clausen / Lobachevsky / ImLi₂ special functions            ✅
 Phase 2   Hyper-ideal geometry  (ζ, lᵢⱼ, αᵢⱼ, σᵢ, σᵢⱼ)             ✅
 Phase 3   CGAL Surface_mesh infrastructure + all three functionals
-          (Euclidean, Spherical, HyperIdeal) + analytical Hessians   ✅
+          (Euclidean, Spherical, HyperIdeal)
+          + analytical Hessians for Euclidean + Spherical
+          (HyperIdeal Hessian: symmetric FD — analytic deferred to 9b) ✅
 Phase 4   Newton solver (SimplicialLDLT + SparseQR fallback)
           + Mesh I/O (OFF/OBJ/PLY) + example programs                ✅   68 tests
 Phase 5   Priority-BFS layout + CLI app + JSON/XML serialisation      ✅   95 tests
@@ -24,7 +26,7 @@ Phase 6   Gauss–Bonnet check/enforce, tree-cotree cut graph (2g),
           exact hyperbolic trilateration, layout normalisation        ✅  121 tests
 Phase 7   MobiusMap, halfedge_uv, Möbius holonomy (SU(1,1)),
           period matrix τ∈ℍ + SL(2,ℤ) reduction,
-          fundamental domain parallelogram + tiling                  ✅  158 tests
+          fundamental domain parallelogram + tiling                  ✅  176 tests
 ```
 
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