docs: update mcp-server

[1parado]

What

Updates the @page-agent/mcp setup example to omit LLM_* env variables and directs users to configure the URL, API key, and model in the browser extension.

Closes #(issue)

Type

• Breaking change
• Bug fix
• Feature / Improvement
• Refactor / Chores
• Documentation / Website / Demo / Testing

Testing

• npm run ci passes
• Tested in modern browsers
• Types/doc added

Validation run:

• npx prettier --check packages/mcp/README.md passes.
• npm run lint passes.
• npm run typecheck passes after npm run postinstall -w @page-agent/ext.
• npm test passes.
• npm run ci was attempted with Node v24.16.0 and npm 11.13.0, but the format step failed on existing repository-wide Prettier warnings outside this change.

Requirements / 要求

• I have read and follow the Code of Conduct and Contributing Guide . / 我已阅读并遵守行为准则。
• This PR is NOT generated by a bot or AI agent acting autonomously. I have authored or meaningfully reviewed every change. / 此 PR 不是由 bot 或 AI 自主生成的，我已亲自编写或充分审查了每一处变更。

[1parado]

Hi，@gaomeng1900. 如果你有时间的话请你看看这个问题这样解决是否合理，如果你有更好的办法请告诉我，谢谢。

相关issue:
#606

我在本地复现了这个问题，原因是 Page Agent Hub 收到 MCP 传来的 LLM_* 配置时，容易触发扩展端 Agent 重建，导致任务 Task aborted. 并且解决方式其实很简单，只需要在Agent端不给page agent配置URL, KEY,MODEL，在浏览器页配置page agent的URL, KEY, MODEL既可稳定调用MCP。我本地也是Windows + Chromium内核的浏览器。Agent端以claudecode为例:

在Agent端如果配置env（模型url，key，model）会出现中断，无响应的现象：

在Agent端只配置MCP信息，不配置模型参数:

为了验证该错误，再次加上env之后:

所以推荐在docs下，将示例改为:
{
"mcpServers": {
"page-agent": {
"command": "npx",
"args": ["-y", "@page-agent/mcp"]
}
}
}
并补充说明，需要在浏览器端配置url，key，model.