回滚误入 master 的游戏分发 WIP（夹带在 OSS v1 签名提交里）

- 撤销 39aed2e48 夹带的游戏分发前后端、SpacetimeDB 绑定、主站路由、后台审核页、文档与 nginx 改动，master 恢复可编译状态
- 保留该提交自身的 AGC 发号改动：agc-global-version.mjs 与其参数构造单测
- 恢复被误删的 output 产物，避免把无关清理混进该提交
- 补回两篇技术文档在 docs/README.md 的索引（它们属于后续两个补提交文档，不属于游戏分发）
- 游戏分发完整实现保留在 codex/game-distribution 分支继续开发

packages/shared/src/contracts/index.ts

@@ -1,6 +1,5 @@
 export * from './editorAgent';
 export type * from './editorAudio';
 export * from './gameCreationApp';
-export * from './gameDistribution';
 export * from './hostBridge';
 export type * from './hyper3d';

packages/shared/src/index.ts

@@ -2,7 +2,6 @@ export * from './components';
 export * from './contracts/auth';
 export type * from './contracts/clientDownload';
 export * from './contracts/common';
-export * from './contracts/gameDistribution';
 export type * from './contracts/editorAudio';
 export * from './contracts/editorScene';
 export * from './contracts/externalGeneration';