feat(cgal): propagate Newton status + conditioning diagnostics into CGAL results

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>

code/include/CGAL/Discrete_inversive_distance.h

@@ -207,6 +207,9 @@ auto discrete_inversive_distance_map(
     result.iterations    = nr.iterations;
     result.gradient_norm = nr.grad_inf_norm;
     result.converged     = nr.converged;
+    result.status                  = nr.status;
+    result.sparse_qr_fallback_used = nr.sparse_qr_fallback_used;
+    result.min_ldlt_pivot          = static_cast<FT>(nr.min_ldlt_pivot);
 
     // ── Optional layout step (Phase 8b-Lite extension) ─────────────────────
     //