添加 AGC 客户端更新检查与下载能力 (#230)

实现 AGC 启动版本检测与 OSS 安装包下载。

- 每次客户端打开时从 OSS latest.json 检查新版本
- 新版本提示支持 releaseNotes，并通过 Tauri 命令下载到系统下载目录
- 下载地址限制受信任 OSS、HTTPS、大小与可选 SHA-256 校验
- 补充 Tauri capability/CSP、单测和发布文档

Closes #224

Reviewed-on: http://192.168.35.82/git/GenarrativeAI/Genarrative/pulls/230

package.json

@@ -171,6 +171,7 @@
     "ai-game-creator-shell:dev": "npm --prefix apps/ai-game-creator-shell run dev",
     "ai-game-creator-shell:dev-server": "npm --prefix apps/ai-game-creator-shell run dev-server",
     "ai-game-creator-shell:build": "npm --prefix apps/ai-game-creator-shell run build --",
+    "ai-game-creator-shell:release:upload": "npm --prefix apps/ai-game-creator-shell run release:upload",
     "ai-game-creator-shell:llm-status": "npm --prefix apps/ai-game-creator-shell run llm-status --",
     "ai-game-creator-shell:agent-task": "npm --prefix apps/ai-game-creator-shell run agent-task --",
     "agc:chat": "npm --prefix apps/ai-game-creator-shell run chat --",