Initial release: game-studio plugin for Claude Code

Repackaged from OpenAI's game-studio Codex plugin (MIT) for Claude Code.

Changes from upstream:
- Added .claude-plugin/plugin.json (Claude Code plugin manifest)
- Removed .codex-plugin/plugin.json (Codex CLI specific)
- Removed skills/*/agents/openai.yaml (Codex CLI specific)
- Added scripts/requirements.txt (Pillow dependency for sprite-pipeline)
- Added Chinese README with installation guide

.claude-plugin/plugin.json

@@ -0,0 +1,24 @@
+{
+  "name": "game-studio",
+  "version": "0.1.0",
+  "description": "Design, prototype, and ship browser games with guided 2D and 3D workflows, asset pipelines, and playtesting support.",
+  "author": {
+    "name": "OpenAI",
+    "email": "support@openai.com",
+    "url": "https://openai.com/"
+  },
+  "homepage": "https://openai.com/",
+  "repository": "https://github.com/openai/plugins",
+  "license": "MIT",
+  "keywords": [
+    "games",
+    "phaser",
+    "threejs",
+    "react-three-fiber",
+    "gltf",
+    "rapier",
+    "webgl",
+    "sprites",
+    "playtest"
+  ]
+}