无法添加仓库

```
[W] github Error: Unprocessable Entity
at [cordis.invoke] (/koishi/node_modules/@cordisjs/plugin-http/lib/index.cjs:340:23)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
at async GitHub.request (/koishi/node_modules/koishi-plugin-github/lib/index.js:77:20)
at async _Command. (/koishi/node_modules/koishi-plugin-github/lib/command.js:68:28)
at async Array. (/koishi/node_modules/@koishijs/core/lib/index.cjs:1083:14)
at async _Command.execute (/koishi/node_modules/@koishijs/core/lib/index.cjs:1097:22)
at async /koishi/node_modules/@koishijs/core/lib/index.cjs:2064:22
at async Proxy.withScope (/koishi/node_modules/@koishijs/core/lib/index.cjs:1973:22)
at async next (/koishi/node_modules/@koishijs/core/lib/index.cjs:829:16)
at async Processor._handleMessage (/koishi/node_modules/@koishijs/core/lib/index.cjs:840:22)

```

Start with the repository-add command in koishi-plugin-github/lib/command.js and the GitHub request wrapper in koishi-plugin-github/lib/index.js, then reproduce the reported Unprocessable Entity error. Determine which repository-add input or API response causes the failure and verify that a repository can be added successfully.

Written by the indexing model from the issue text.