Third independent review: persistence boundary

The second correction still overclaims multimodal support. Inspection of the actual persistence boundary found:

• hermes_state.py types api_content as Optional[str] and writes non-string values as None (around lines 5632–5750 and 6078–6106);
• run_agent.py discards non-string _row_api_content during flush (around lines 2104–2110);
• agent/turn_context.py exposes string-only sidecar helpers.

Thus a list sidecar is replayed within the in-memory loop but disappears after persistence/resume, invalidating the claimed durable byte stability. Make the smallest compatible correction: fail closed for non-string content and do not attach the model status on unsupported multimodal/list messages. Do not widen the database schema or persistence contract in this experiment.

Update tests to assert list, empty, mapping, and numeric values are rejected by the same production helper, and that string sidecars remain stable across three requests. Remove any multimodal-support claim from code comments and the report. Run the focused tests, the existing replay/cache regression set, compilation, and git diff --check; update the report with exact results.

Do not edit the book, commit, push, or claim downstream task improvement.