Not authenticated error when out of budget

Im out of budget, and i now get the error this error loading my application that uses the SDK -
```
2026-08-21 11:49:00.627 [Information] Cockpit.Features.Auth.AuthCheckFeature: Auth re-check: restarting SDK client
2026-08-21 11:49:00.627 [Information] Cockpit.Features.Sdk.CopilotClientFeature: Stopping CopilotClient
2026-08-21 11:49:10.668 [Information] Cockpit.Features.Sessions.SessionFeature: Client disconnected — resetting SDK state for active sessions
2026-08-21 11:49:10.668 [Information] Cockpit.Features.Sdk.CopilotClientFeature: Initializing CopilotClient (logLevel=info, telemetry=True)
2026-08-21 11:49:10.669 [Information] Cockpit.Features.Sessions.SessionFeature: SDK state reset complete after client disconnect
2026-08-21 11:49:10.669 [Information] Cockpit.Features.Sdk.CopilotClientFeature: SDK telemetry exporting to C:\Users\c773975\AppData\Local\Cockpit\telemetry\otel-20260821.jsonl
2026-08-21 11:49:10.669 [Information] Cockpit.Features.Sdk.CopilotClientFeature: CopilotClient.StartCliServerAsync starting Copilot CLI. CliPath=C:\Program Files\Cockpit\runtimes\win-x64\native\copilot.exe, Executable=C:\Program Files\Cockpit\runtimes\win-x64\native\copilot.exe, CliPathSource=Bundled, UseStdio=True, Port=(null)
2026-08-21 11:49:11.826 [Information] Cockpit.Features.Sdk.CopilotClientFeature: CopilotClient started successfully
2026-08-21 11:49:11.826 [Information] Cockpit.Features.Sessions.SessionFeature: Client reconnected — resuming current session
2026-08-21 11:49:11.905 [Warning ] Cockpit.Features.Auth.AuthCheckFeature: Auth check: not authenticated — Not authenticated
2026-08-21 11:49:11.905 [Warning ] Cockpit.Features.Sdk.CopilotClientFeature: JsonRpc.InvokeAsync JSON-RPC request finished. Elapsed=00:00:00.0791917, Method=models.list, RequestId=2, Status=Failed
GitHub.Copilot.RemoteRpcException: Request models.list failed with message: Not authenticated. Please authenticate first.
at GitHub.Copilot.JsonRpc.InvokeAsync[T](String method, Object[] args, CancellationToken cancellationToken, Action`1 onResponseInline)
2026-08-21 11:49:11.906 [Error ] Cockpit.Features.Models.ModelFeature: Failed to fetch model list from Copilot SDK
System.IO.IOException: Communication error with Copilot CLI: Request models.list failed with message: Not authenticated. Please authenticate first.
---> GitHub.Copilot.RemoteRpcException: Request models.list failed with message: Not authenticated. Please authenticate first.
at GitHub.Copilot.JsonRpc.InvokeAsync[T](String method, Object[] args, CancellationToken cancellationToken, Action`1 onResponseInline)
at GitHub.Copilot.JsonRpc.InvokeAsync[T](String method, Object[] args, CancellationToken cancellationToken, Action`1 onResponseInline)
at GitHub.Copilot.CopilotClient.InvokeRpcAsync[T](JsonRpc rpc, String method, Object[] args, StringBuilder stderrBuffer, CancellationToken cancellationToken, Action`1 onResponseInline)
--- End of inner exception stack trace ---
at GitHub.Copilot.CopilotClient.InvokeRpcAsync[T](JsonRpc rpc, String method, Object[] args, StringBuilder stderrBuffer, CancellationToken cancellationToken, Action`1 onResponseInline)
at GitHub.Copilot.CopilotClient.ListModelsAsync(CancellationToken cancellationToken)
at Cockpit.Features.Models.ModelFeature.GetModels(CancellationToken cancellationToken) in D:\a\Cockpit\Cockpit\src\Cockpit\Features\Models\ModelFeature.cs:line 48
```

Im out of budget on my enterprise account i get the above error.
I signed out and then into my personal account, it loads without an issue.

Im unable to add budget to my enterprise account to prove that the `Not authenticated` error is misleading/ wrong.
But I did sign back into my enterprise account still get the same error

Start at src/Cockpit/Features/Models/ModelFeature.cs line 48 and trace the models.list failure after AuthCheckFeature restarts the client. Compare the over-budget enterprise-account behavior with the successful personal-account login; done when the resulting error accurately reflects the authentication or budget state and the client recovery path is covered.

索引モデルが issue の本文から書いたものです。