Seed approved structure: design SSOT, operator docs, scaffolds.

Product layout for Lumina / Salon_Assistant at 0.1.0-design.
No product implementation until explicit build.

docs/ARCHITECTURE.md

@@ -0,0 +1,21 @@
+# Architecture (operator summary)
+
+Full design: **[design/DESIGN_PLAN.md](../design/DESIGN_PLAN.md)**.
+
+## Layers
+
+```text
+Host (bootstrap, Docker, product scripts, nemohermes/openshell CLIs)
+  → OpenShell gateway (credentials, L7 policy, sandbox lifecycle)
+    → Hermes sandbox (minimal Lumina profile)
+         skills, channels, MCP clients (allowlisted)
+  → External OpenAI-compatible model (outside containers OK)
+```
+
+## Related design docs
+
+- [Planes](../design/planes.md)  
+- [Det vs inference](../design/det-vs-inf.md)  
+- [MCP integrations](../design/mcp-integrations.md)  
+- [Updates lifecycle](../design/updates-lifecycle.md)  
+- [Platform research notes](../design/research/platform-notes.md)