Clean up architecture specs: remove stale references, align docs with code, improve readability
- Replace stale DD references (DD3, DD6, DD9, DD10) with proper ADR links
- Fix 'Open Question 1' → OQ-01/OQ-03 cross-references
- Rewrite metagraph-module.md 'Why TypeBox Modules' to describe capabilities
directly instead of framing as SchemaBuilder replacement
- Remove 'Transition from SchemaBuilder' section, replace with Source Structure
- Clean up implementation path: strikethrough phases → status table
- Fix data model diagram: remove non-existent nodeTypeId, fix EdgeType label
- Align EdgeConstraints examples with actual code (add default values)
- Clarify validateNode/validateEdge error behavior in docs
- Align EncryptedDataSchema code example with actual implementation
- Fix overview.md: correct dependency table, update current state, fix TypeBox URL
- Fix forward-look.md garbled text about dbtype element migration
- Fix open-questions.md: correct OQ count (4→7 open), add summary table
- Update doc statuses: schema-evolution, encrypted-data, open-questions → reviewed
- Update AGENTS.md to reflect current implementation state