[engine-failure] PROJ-873-llmxive-follow-up-extending-active-learn @ tasks: RuntimeError

Automated report (spec 023 / FR-016) — an unexpected engine failure occurred while processing **PROJ-873-llmxive-follow-up-extending-active-learn** at stage `tasks`.

```
RuntimeError: LLMReviewer[coverage]: 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: coverage\nreviewer_kind: llm\nstage: tasked\nartifact_path: projects/PROJ-873-llmxive-follow-up-extending-active-learn/tasks.md\nartifact_hash: a6f19425b0a8e6d6c6999999999999999'
```

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 engine-failure report and the review frontmatter for projects/PROJ-873-llmxive-follow-up-extending-active-learn/tasks.md. Trace how the `tasks` stage handles the LLMReviewer[coverage] result, then verify that a contentless or truncated review cannot count as acceptance and that the normal retry remains schedulable.

Written by the indexing model from the issue text.