read_result() returns cases/provenance for the old bare-list receipts and
the new schema-2 object, and rejects unknown schemas. Existing evidence
(e.g. 70f6617) and its digest scripts stay valid for schema 1; queue and
digest scripts must use read_result(...)['cases'] for new receipts.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>