Rearrange code and cleanup

include/boxes/diagnostics.h

@@ -0,0 +1,20 @@
+#ifndef BOXES_DIAGNOSTICS_H
+#define BOXES_DIAGNOSTICS_H
+
+#include "editor/decl.h"
+#include "io/ui.h"
+#include "pch.h"
+#include "utils/utils.h"
+
+struct DiagnosticBox {
+  std::vector<VWarn> warnings;
+  std::vector<ScreenCell> cells;
+  uint32_t box_width;
+  uint32_t box_height;
+
+  void clear();
+  void render_first();
+  void render(Coord pos);
+};
+
+#endif