[engine-failure] PROJ-914-llmxive-follow-up-extending-macaron-a2ui @ tasks: RuntimeError

Automated report (spec 023 / FR-016) — an unexpected engine failure occurred while processing **PROJ-914-llmxive-follow-up-extending-macaron-a2ui** 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-914-llmxive-follow-up-extending-macaron-a2ui/specs/001-llmxive-follow-up-extending-macar'
```

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 by tracing the engine-failure report for project PROJ-914 at the `tasks` stage and inspect the `LLMReviewer[constraint_preservation]` review output. Determine why the review frontmatter lacks `verdict:` or `concerns:`/`action_items:`; done means contentless or truncated reviews cannot count as acceptance and the normal retry completes successfully.

Written by the indexing model from the issue text.