refactor(api): consistent naming for spherical + hyper-ideal helpers (A1–A3)

Standardize the low-level free-function API on <verb>_<geom>_<rest>,
matching the already-consistent setup_<geom>_maps. Old names kept as
[[deprecated]] inline aliases for one release; all internal call sites
migrated.

Renames:
  assign_vertex_dof_indices      -> assign_spherical_vertex_dof_indices
  assign_all_spherical_dof_indices -> assign_spherical_all_dof_indices
  assign_all_dof_indices         -> assign_hyper_ideal_all_dof_indices
  compute_lambda0_from_mesh      -> compute_spherical_lambda0_from_mesh
  gradient_check                 -> gradient_check_hyper_ideal

A4/A5 (public CGAL API) intentionally deferred pending the license/
provenance decision (see CGAL submission audit G0/G1).

Verified: 277/277 CGAL tests pass, no deprecation warnings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

code/include/newton_solver.hpp

@@ -384,7 +384,7 @@ inline NewtonResult newton_spherical(
 ///
 /// DOF layout: first V_free entries are vertex variables b_v (hyper-ideal radii),
 /// followed by E entries for edge variables a_e (intersection angles).
-/// Use assign_all_dof_indices(mesh, maps) to set v_idx and e_idx automatically —
+/// Use assign_hyper_ideal_all_dof_indices(mesh, maps) to set v_idx and e_idx automatically —
 /// no vertex needs to be pinned.
 ///
 /// \param mesh      Input triangulated surface, genus g ≥ 1.