[engine-failure] PROJ-828-llmxive-follow-up-extending-learning-to @ tasks: RuntimeError

Automated report (spec 023 / FR-016) — an unexpected engine failure occurred while processing **PROJ-828-llmxive-follow-up-extending-learning-to** at stage `tasks`.

```
RuntimeError: LLMReviewer[executability]: 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: rq_validity\nreviewer_kind: llm\nstage: tasks_review\nartifact_path: projects/PROJ-828-llmxive-follow-up-extending-learning-to/specs/001-llmxive-follow-up-extending-learning-to'
```

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 LLMReviewer executability stage for PROJ-828 and inspect the review frontmatter shown in the RuntimeError, including the artifact under projects/PROJ-828-llmxive-follow-up-extending-learning-to/specs/001-llmxive-follow-up-extending-learning-to. Reproduce the tasks-stage retry and determine why a truncated review reaches validation; done means the retry no longer fails on contentless review output and the false-convergence guard remains effective.

Written by the indexing model from the issue text.