Most of the Tower/Tenrouirai system is already implemented on develop.
This doc captures what works, what is broken (PostTenrouirai Op=1 no-op,
block2 never written, PresentBox empty), and the remaining unknown packet
fields — so future contributors know exactly where to focus effort.
Also updates unimplemented.md to note the feature/tower branch was
superseded by direct integration into develop.
