Schema versioning future plan

[talkasab]

Summary

Introduce schema versioning tied 1:1 to package versions, with backward compatibility handled by the manifest retaining old schema DBs. This adds a _metadata table to built DBs, upgrades manifest format to v2 (array of schema entries per package), and teaches packages to select the DB matching REQUIRED_SCHEMA.

Scope / Deliverables

• Add _metadata table to findingmodel/anatomic DB builds (schema_version, content_version, built_at, record_count).
• Upgrade manifest format to v2.0 (package-specific manifest with entries array) and update readers/writers.
• Add REQUIRED_SCHEMA constants to packages and selection logic for matching schema.
• Update publish flow to read schema_version from DB metadata and update the correct manifest entry.

Task Reference

See tasks/schema-versioning-future.md.