Route prepared file targets through platform services

src/platform_windows/windows_platform_services.cpp

@@ -448,6 +448,19 @@ public:
         invoke_selected_path(path, callback);
     }
 
+    [[nodiscard]] pp::platform::PreparedFileTarget prepare_writable_file(
+        std::string_view type,
+        std::string_view default_name,
+        std::string_view data_path,
+        std::string_view temporary_path) override
+    {
+        (void)type;
+        (void)default_name;
+        (void)data_path;
+        (void)temporary_path;
+        return {};
+    }
+
     void save_prepared_file(
         std::string_view path,
         std::string_view suggested_name,