docs: NextGraph multi-user data model — stores, auth matrix, inbox fork plan

Capture the multi-user design exploration as project knowledge + briefs:
- knowledge: NextGraph store types/permissions (+ inbox at protocol, SDK
  exposure, local repo path); integration model (iframe, where the verifier
  runs, generic JS plumbing, ngd stateful, build-time broker target)
- briefs: multi-store refactor; authorization matrix + query inventory +
  derived store partitions; temporary fork to expose the inbox (3 layers:
  SDK fork, Coolify self-hosting, Festipod integration; libs via build:ng)
- fix stale @ng-org versions (alpha.11 -> alpha.13) and a broken
  decision-record link in data-layer.md

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -68,8 +68,11 @@ bun run build:orm        # Regenerate ORM from SHEX shapes
 - [Test Layer Contracts](.project/knowledge/test-layer-contracts.md) — what each of `@ui`/`@data`/`@e2e` is allowed to test
 - [Screens](.project/knowledge/screens.md) — screen inventory, registry, sketchy components
 - [Data-Layer Testing](.project/knowledge/data-layer-testing.md) — real broker testing, wallet setup, Playwright harness, e2e layer
+- [Stores NextGraph et droits d'accès](.project/knowledge/nextgraph-stores-permissions.md) — fiche de référence des 5 types de stores et de leurs permissions
+- [Modèle d'intégration NextGraph](.project/knowledge/nextgraph-integration-model.md) — paquets JS, modèle iframe, où tourne le verifier, reciblage du broker
 
 ## Briefs (work not yet started)
 
 - [Multi-store refactor](.project/briefs/multi-store-refactor.md) — passer du mono-store actuel à une structure de Group stores par communauté/event/RDV (prérequis multi-user)
 - [Matrice d'autorisations et requêtes](.project/briefs/authorization-matrix.md) — analyse qui doit guider la structure de stores cible
+- [Forker NextGraph pour l'inbox](.project/briefs/fork-nextgraph-inbox.md) — patcher nextgraph-rs pour exposer l'inbox au SDK JS (notification d'inscription)