[engine-failure] PROJ-434-predicting-plant-root-architecture-from- @ tasks: RuntimeError

Automated report (spec 023 / FR-016) — an unexpected engine failure occurred while processing **PROJ-434-predicting-plant-root-architecture-from-** 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-434-predicting-plant-root-architecture-from-/specs/001-predicting-plant-root-architectur'
```

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 automated report for spec 023 / FR-016 and trace the `tasks` stage around `LLMReviewer[constraint_preservation]`. Check how review frontmatter is handled when it lacks `verdict:` and `concerns:`/`action_items:`. Done means contentless or truncated reviews cannot count as acceptance and the reported engine failure no longer occurs.

Written by the indexing model from the issue text.