Frequent and Unrecoverable State after Server-side Errors

报告中未标识源文件、测试或入口点。首先使用 Copilot for Xcode 0.46.157、Language Server 1.403.0、Xcode 16.2 和 macOS 15.6.1 重现故障，然后跟踪服务器端错误后的会话和 UI 状态。当无需退出登录或重启 macOS，提示和响应即可恢复，并且模型选择也得到恢复时，即表示完成。

Describe the bug
I am encountering frequent and varied server-side errors during normal usage of Copilot for Xcode. Once any of these errors occur, Copilot enters a non-functional state: it can no longer send new prompts or receive responses.

At this point, the only temporary recovery methods are:
• signing out and back into GitHub Copilot, or
• restarting macOS entirely.

However, the issue consistently reoccurs within a short time window, often within the same day.

Additionally, after attempting recovery, Copilot sometimes fails to reinitialize its UI state correctly. For example:
• the model selection UI is missing, leaving no way to select or confirm a model
• sending prompts does not trigger any loading or response state at all

This suggests a form of session or service state corruption that Copilot is unable to detect or recover from automatically.

Versions

• Copilot for Xcode: 0.46.157 with Language Server 1.403.0
• Xcode: 16.2
• macOS: 15.6.1

Steps to reproduce
1. Use Copilot for Xcode under normal development workflows.
2. The issue occurs intermittently but with high frequency over time.
3. Restarting macOS temporarily restores functionality.
4. The issue reappears after continued usage.

Screenshots

Logs
No relevant Copilot logs could be found in local log folders (No folder for GitHub Copilot).

Additional context
• I frequently use a VPN; however:
• GitHub.com works reliably.
• GitHub Copilot works reliably in VS Code under the same network conditions.
• The issue appears to be specific to Copilot for Xcode rather than general connectivity.