rnd-ash/ultimate-nag52-fw — reverse-engineered prompt

Build me the firmware project for an Ultimate NAG52 722.6 transmission control unit, using the existing C++ codebase and keeping it focused on the real hardware this repo targets.

I want it to compile cleanly, have the PlatformIO and CMake setup working, and keep the current diagnostics, partition layout, memory map, and generated data scripts wired in properly. Make sure the documentation generation still works with Doxygen and the bundled theme submodule. Don’t add random car features or unsafe behavior, just preserve and organize what’s already here so someone can build, test, and flash the firmware in a reliable way.

Please also add clear notes in the README about setup, building, generating docs, and the important warning that the TCU can be bricked if the update guide is not followed. Look up the current PlatformIO and Doxygen docs online if you need to.