clean split

src/README.md

@@ -66,6 +66,7 @@ Included now:
 - app-owned display/render layer model for shader build readiness
 - app-owned submission of a completed shader artifact
 - render-thread-owned render-content interface with runtime shader content as the default implementation
+- app-owned runtime-content controller interface with the Slang shader stack as the default implementation
 - render-thread-owned runtime render scene for ready shader layers inside the default render-content adapter
 - shared-context GL prepare worker for runtime shader program compile/link
 - render-thread-only GL program swap once a prepared program is ready
@@ -265,6 +266,12 @@ The HTTP server runs on its own thread. `control/http/HttpControlServer` owns so
 
 `control/osc/OscControlServer` is currently a lifecycle/status stub. It consumes the startup OSC config and reports whether OSC is configured or disabled, but it deliberately does not open a UDP socket or dispatch parameter changes yet.
 
+## Runtime Content Boundary
+
+`app/RenderCadenceApp` owns startup, video output, preview, telemetry, OSC status, and HTTP server lifetime. It does not own the Slang shader stack directly. Runtime content is supplied through `IRuntimeContentController` in `app/RuntimeContentController.h`.
+
+The default implementation is `ShaderRuntimeContentController`. It wraps `RuntimeLayerController`, exposes shader catalog/layer state to `/api/state`, handles the shader layer POST commands, and publishes render-ready shader layers to the current render thread. A fork that uses a D3D engine should replace this controller with a D3D engine controller and decide separately whether to keep the current GL render/readback thread as a bridge or replace it with a D3D-native frame publisher.
+
 ## Optional DeckLink Output
 
 DeckLink output is an optional edge service in this app.