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

docs/architecture/open-questions.md

@@ -1,6 +1,6 @@
 ---
-status: draft
-last_updated: 2026-05-29
+status: reviewed
+last_updated: 2026-05-30
 ---
 
 # Open Questions Tracker
@@ -9,6 +9,26 @@ Cross-cutting compilation of all unresolved questions across the storage archite
 
 When a question is resolved, update its status to `resolved` and add a resolution note. Once all questions in a theme are resolved, the theme section can be removed and the resolution noted in the relevant ADR.
 
+## Summary
+
+| Status | Count |
+|--------|-------|
+| Open | 7 |
+| Partially resolved | 1 |
+| Resolved | 8 |
+
+**Open questions requiring decisions:**
+- **OQ-03** (actors table design) — deferred to ACL design
+- **OQ-04** (repository layer host-specific vs host-agnostic) — start host-specific
+- **OQ-07** (encryptRaw performance) — low priority, add if needed
+- **OQ-10** (Edit[] classification) — needs POC
+- **OQ-11** (auto-migrate vs explicit consumer action) — conditional on OQ-10
+- **OQ-12** (schema evolution vs event-sourced replay) — post-v1 concern
+- **OQ-13** (schema evolution events in event stream) — post-v1
+
+**Partially resolved:**
+- **OQ-01** (flowgraph Module export) — storage can start without it
+
 ## How to Use This Document
 
 - Each question has an **ID** (e.g., OQ-01), **status**, **origin** (which doc(s)), and **priority**