layout: restructure into src/ tests/ android/ scripts/ tools/

- extension/src/{port,platform,codepage} -> src/; native_render -> src/host
  (+ dxt, shaders/); libgr2 -> src/gr2; extension/third_party -> third_party
- extension/tests -> tests/port, libgr2/tests -> tests/gr2
- android-native -> android (build.sh, push-client.sh moved in)
- script -> scripts; tools/40250 -> tools/server; oracle -> tools/granny-oracle;
  perf tools -> tools/perf
- all build trees under build/ (native, release, android, port-gate)
- xrender:: CMake aliases -> mt::; port-map ledger impl paths rewritten

No code changes. ctest 15/15, port_gate macos+android PASS, port_map check 0 errors.

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

audit/contracts/world.reset-cleanup.md

@@ -119,7 +119,7 @@
 
 ## Regression evidence
 
-- `extension/tests/net_entity_test.cpp`：map reset 丢弃实体、地面、目标、飞行、飞行目标和特效队列。
+- `tests/port/net_entity_test.cpp`：map reset 丢弃实体、地面、目标、飞行、飞行目标和特效队列。
 - `project/fly_reset_test.gd`：活动弹道、弹道视觉和爆点视觉在 map reset 后全部消失。
 - `project/screen_hp_bar_test.gd`：实体/HP 条的 map reset 清理。
 - `project/net_world_reset_test.gd`：模型升级队列、聊天尾标、target/hover 引用和 live actor 的 Loading 清理；修复前失败 3 项，修复后通过。