[engine-failure] PROJ-373-predicting-rate-constants-of-sn1-reactio @ tasks: RuntimeError

Automated report (spec 023 / FR-016) — an unexpected engine failure occurred while processing **PROJ-373-predicting-rate-constants-of-sn1-reactio** 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: task_executability\nreviewer_kind: llm\nstage: tasks\nartifact_path: projects/PROJ-373-predicting-rate-constants-of-sn1-reactio/specs/001-predicting-rate-constants-of-sn1-react'
```

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 at the LLMReviewer executability check for stage `tasks` and inspect the review frontmatter for the referenced PROJ-373 artifact path. Trace how a review lacking `verdict:` or `concerns:`/`action_items:` is handled during retry scheduling. Done means a contentless or truncated review cannot count as acceptance while the project remains schedulable.

Written by the indexing model from the issue text.