Follow-up to S2: surface the new NewtonResult diagnostics through the public
CGAL result types so callers of the high-level API see them too.
- Add `CGAL::Newton_status` (alias of conformallab::NewtonStatus) and three
fields — `status`, `sparse_qr_fallback_used`, `min_ldlt_pivot` — to
Conformal_map_result, Hyper_ideal_map_result and Circle_packing_result.
(sparse_qr_fallback_used already existed on Conformal_map_result but was never
populated; it is now wired through.)
- Map them from NewtonResult at all five entry points (euclidean / spherical /
hyper_ideal / inversive_distance / cp_euclidean).
- Test: SingleTriangleConverges now asserts status == Converged and the
diagnostics propagate.
Additive only — existing `converged`/`iterations`/`gradient_norm` semantics
unchanged. 301/301 CGAL tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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