Add db merged with exact account/chat/local-ID selection and shard ambiguity checks. Preserve Int64 composite message types and parse bounded, DTD-free embedded record XML, including duplicate messages and source metadata. Revalidate cached keys against current page-1 HMAC; replace the SQL write probe with sqlite3_db_readonly. Core tests: 129 passed. Windows Session 0 database validation: 5/5; all 16 text/sender/source-ID/timestamp entries matched independent XML parsing. Read-only UI baseline: 3/3; zero sends.
