docs: clarify presentation layer is REST-only

docs/superpowers/specs/2026-05-14-v2-rewrite-design.md

@@ -20,7 +20,7 @@ crates/
   domain/                  # entities, value objects, ports (traits), domain events
   application/             # use cases (commands + queries), no framework deps
   api-types/               # request/response DTOs, shared serializable types
-  presentation/            # axum handlers, routes, extractors, state, openapi
+  presentation/            # axum handlers, routes, extractors, state, openapi — JSON REST only, no HTML rendering (client is Next.js)
   worker/                  # event consumer loop, dispatches to event handlers
   adapters/
     postgres/              # sqlx impls of all repos + migrations/