Removes the only architectural lock-in spotted in the MVP audit before
Phase 9a starts: the wrapper hard-coded Simple_cartesian<double> as the
kernel inside discrete_conformal_map_euclidean. This would have broken
any Surface_mesh<P> where P came from a different kernel (e.g. EPIC).
Change
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* CGAL::Kernel_traits<typename TriangleMesh::Point>::Kernel is now used
to deduce the kernel from the mesh's point type.
* The full Default_traits<...> instantiation is wrapped in
internal_np::Lookup_named_param_def so a future `geom_traits(...)`
named parameter can override the entire traits class without changes
to the wrapper body (CGAL idiom, used by every CGAL package).
* New test `KernelIsDeducedFromMeshPointType` pins the contract
explicitly with static_asserts.
Why now
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Phase 9a (Inversive-Distance) will copy this same template pattern.
Fixing the kernel deduction once here keeps the design free for any
user kernel; doing it after 9a would mean two parallel hard-coded
kernel sites to refactor.
Tests
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CGAL suite: 184/184 passed, 0 skipped (was 183).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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