Document the new DPF surfaces in one command set, and test the field, half-tree, and multipoint edges.

Co-authored-by: Cursor <cursoragent@cursor.com>

include/grotto/gadgets/binary/countl_zero.hpp

@@ -20,7 +20,11 @@ namespace grotto
 namespace gadgets
 {
 
-struct countl_zero
+HEDLEY_DIAGNOSTIC_PUSH
+HEDLEY_DIAGNOSTIC_DISABLE_DEPRECATED
+
+
+struct HEDLEY_DEPRECATED_FOR(2026, grotto::exact_constant) countl_zero
 {
     template <typename T>
     T operator()(T x)
@@ -43,6 +47,8 @@ struct gadget_hints<countl_zero>
     static constexpr std::array<double, degree+1> hint_canonical_polys[] = { };
 };
 
+HEDLEY_DIAGNOSTIC_POP
+
 }  // namespace gadgets
 
 }  // namespace grotto