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>

libgr2/README.md

@@ -17,7 +17,7 @@
 ## 验证
 
 - 全量 9166 个 Metin2 `.gr2`：**0 崩溃、0 非退化谓词失败**（`tools/gr2fuzz`）
-- **对拍真 Granny 2.9.12**：骨骼世界矩阵 ≤ 4.6e-5、蒙皮顶点 ≤ 6.5e-5（`tools/oracle_diff`，`test/m2-numeric.json`，23 用例含 v7 / 双 root / 刚体 / 多动画帧）
+- **对拍真 Granny 2.9.12**：骨骼世界矩阵 ≤ 4.6e-5、蒙皮顶点 ≤ 6.5e-5（`tools/oracle_diff`，`oracle/m2-numeric.json`，23 用例含 v7 / 双 root / 刚体 / 多动画帧）
 - 坏输入（空 / 错 magic / 截断 / 越界索引）一律干净报错，不崩
 
 ## 明确不做（Metin2 语料里 0 出现；要「任意 gr2」才需要）