xcode mcp server tool calls are failing

### Describe the bug

I have added xcode mcp server as documented on apple's developer documentation: https://developer.apple.com/documentation/xcode/giving-agentic-coding-tools-access-to-xcode

But the calls are failing in copilot.

### Affected version

1.0.12

### Steps to reproduce the behavior

1. Run `/mcp add` in copilot cli
2. Give name of server: xcode
3. Select server Type: STDIO
4. Give command: xcrun mcpbridge
5. Leave environment variables and tools as default
6. It should look something like this:

7. Save it
8. Try to use xcode mcp server in copilot cli

### Expected behavior

MCP calls dont fail

### Additional context

_No response_

首先，使用 `xcrun mcpbridge` STDIO 命令以及默认的环境变量和工具，通过 `/mcp add` 流程复现该故障。从该入口点开始跟踪 Copilot CLI 的 MCP 调用处理，然后验证已配置的 Xcode 服务器调用能够成功完成，而不是失败。

由索引模型根据 Issue 内容生成。