Move prepared-file work into app runtime

src/legacy_canvas_draw_merge_services.h

@@ -250,6 +250,19 @@ template <typename GridT>
     };
 }
 
+template <typename ModesT>
+[[nodiscard]] inline auto make_legacy_canvas_draw_merge_current_modes_draw(
+    ModesT* modes,
+    const glm::mat4& ortho_proj,
+    const glm::mat4& proj,
+    const glm::mat4& camera)
+{
+    return [modes, ortho_proj, proj, camera] {
+        for (auto& mode : *modes)
+            mode->on_Draw(ortho_proj, proj, camera);
+    };
+}
+
 struct LegacyCanvasDrawMergeSmaskFacesExecution {
     std::function<void()> set_active_texture_unit;
     std::function<void()> enable_blend;