cleanup: remove Godot-era test data, formats/, dead proto reader and duplicates

- test/: bgfx/Godot render goldens and compare shots nothing reads any more;
  the Granny oracle result m2-numeric.json moves to oracle/
- formats/: only the .spt sniffer was still linked; it moves into
  platform/SpeedTreeLib, the rest and tools/map_probe go
- bgm/ duplicated Client/BGM byte for byte; tools/root archived root scripts
  that root.epk already holds; extension/src/proto had no build reference
- GEMINI.md duplicated AGENTS.md

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CMakeLists.txt

@@ -17,7 +17,6 @@ option(MT_BUILD_PORT "Build the 40250 port and its tests" ON)
 option(MT_BUILD_NATIVE_RENDER "Build the SDL3 and Vulkan client" OFF)
 
 add_subdirectory(libgr2)
-add_subdirectory(formats)
 add_subdirectory(extension/third_party)
 add_subdirectory(extension/src/codepage)
 if(MT_BUILD_PORT OR MT_BUILD_NATIVE_RENDER)