[engine-failure] PROJ-777-analyzing-the-trade-off-between-prompt-s @ spec: PermanentBackendError

Automated report (spec 023 / FR-016) — an unexpected engine failure occurred while processing **PROJ-777-analyzing-the-trade-off-between-prompt-s** at stage `spec`.

```
PermanentBackendError: Error code: 400 - {'detail': 'Budget has been exceeded! EndUser=848c9f24-ca72-4aea-af34-f48cd3c74755 Current cost: 2.178421, Max budget: 2.0'}
```

The project remains schedulable; it will retry on its normal cadence and recover once the underlying defect is fixed. Closing this issue does not require any project-state change.

Begin with the spec-stage run for spec 023 / FR-016 and trace where PermanentBackendError is produced after the budget check. No source file or test is named in the report. Done means the underlying defect is fixed and the project recovers on its normal retry cadence without exceeding the configured budget.

Written by the indexing model from the issue text.