build: add some forgotten, required, headers

array/darray.hpp

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include "../debug/assert.hpp"
 #include "../iterator/zip.hpp"
 
 #include <iterator>

iterator/iota.hpp

@@ -8,6 +8,9 @@
 
 #pragma once
 
+#include <cstddef>
+#include <iterator>
+
 namespace cruft::iterator {
     ///////////////////////////////////////////////////////////////////////////
     /// A numeric range that supplies a sequence of values.