[engine-failure] PROJ-045-investigating-the-relationship-between-d @ tasks: RuntimeError

Automated report (spec 023 / FR-016) — an unexpected engine failure occurred while processing **PROJ-045-investigating-the-relationship-between-d** at stage `tasks`.

```
RuntimeError: LLMReviewer[constraint_preservation]: review frontmatter has neither `verdict:` nor `concerns:`/`action_items:` — a contentless/truncated review MUST NOT count as acceptance (false-convergence guard). First 200 chars: '```yaml\n---\nreviewer_name: constraint_preservation\nreviewer_kind: llm\nstage: tasks\nartifact_path: projects/PROJ-045-investigating-the-relationship-between-d/specs/001-investigating-the-relationship-be'
```

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.

Start with the LLMReviewer constraint_preservation path involved in spec 023 / FR-016 and inspect how review frontmatter is parsed at the tasks stage. Reproduce the reported RuntimeError and trace the handling of reviews lacking verdict, concerns, or action_items. Done means contentless or truncated reviews cannot count as acceptance and the normal retry can recover.

Written by the indexing model from the issue text.