[engine-failure] PROJ-436-assessing-the-validity-of-statistical-si @ spec: RuntimeError

Automated report (spec 023 / FR-016) — an unexpected engine failure occurred while processing **PROJ-436-assessing-the-validity-of-statistical-si** at stage `spec`.

```
RuntimeError: LLMReviewer[testability]: 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: testability\nreviewer_kind: llm\nstage: specified\nartifact_path: projects/PROJ-436-assessing-the-validity-of-statistical-si/specs/001-assessing-the-validity-of-statistical-si/'
```

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 spec-stage processing for PROJ-436-assessing-the-validity-of-statistical-si and the LLMReviewer[testability] frontmatter validation. Reproduce the failure from spec 023 / FR-016, inspect the review artifact under projects/PROJ-436-assessing-the-validity-of-statistical-si/specs/001-assessing-the-validity-of-statistical-si/, and verify that contentless or truncated reviews do not count as acceptance while valid verdict or concerns/action_items metadata does.

Written by the indexing model from the issue text.