Frequent and Unrecoverable State after Server-side Errors

報告中未識別任何原始檔、測試或進入點。先使用 Copilot for Xcode 0.46.157、Language Server 1.403.0、Xcode 16.2 和 macOS 15.6.1 重現故障，然後追蹤伺服器端錯誤後的工作階段與 UI 狀態。當不需登出或重新啟動 macOS，提示與回應即可復原，且模型選取也一併恢復時，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.