Finalize digital-twin scope as two ACL-based patterns

Plan's digital-twin scope is now exactly (1) environment-lifecycle
promotion via ACL flip on write authority and (2) safe read-only
consumption for KPI / monitoring systems — both delivered by
already-committed architecture. Removes the meeting-prep brief and the
management-delivered use-cases source document; canonical model and
state vocabulary stand as pillar-2 work on their own.

README.md

@@ -40,7 +40,6 @@ The plan also declares a **Unified Namespace (UNS)** composed of OtOpcUa + Redpa
 |---|---|
 | [`current-state/legacy-integrations.md`](current-state/legacy-integrations.md) | Pillar 3 denominator: 3 legacy IT/OT integrations to retire |
 | ~~`current-state/equipment-protocol-survey.md`~~ | Removed — protocol survey no longer needed; OtOpcUa v2 team committed driver list directly |
-| [`goal-state/digital-twin-management-brief.md`](goal-state/digital-twin-management-brief.md) | Digital twin management conversation brief (completed) |
 | [`schemas/`](schemas/) | Canonical OT equipment definitions (DRAFT seed contributed by OtOpcUa team — UNS hierarchy + equipment-class templates + format JSON Schemas + worked FANUC CNC pilot). Temporary location until a dedicated `schemas` repo is created and an owner team is named — see `schemas/README.md` |
 
 ### Output Generation