Remove editor app include root

docs/plan/editor-core-refactor-plan.md

@@ -38,8 +38,9 @@ incomplete:
 
 - `XCEditorCore` now limits its public app include surface to
   `editor/app/Core`, `editor/app/Commands`, `editor/app/State`, and
-  `editor/app/Host`, but the app still carries internal include-path residue
-  and has not yet converged on the final directory names.
+  `editor/app/Host`, and app/core sources now include through explicit module
+  roots instead of a private `editor/app` compatibility root. The app has not
+  yet converged on the final directory names.
 - Feature panels no longer use `Composition/EditorContext.h` directly, but
   app-core tests still need to be restored before the boundary is exercised
   outside the executable host.
@@ -75,13 +76,20 @@ Completed boundary cuts:
   now live under `editor/app/Core/Windowing`, and
   `XCEditorCore` no longer exports the whole `editor/app` root as a public
   include directory.
+- The private `editor/app` compatibility include root is gone from
+  `XCEditorCore` and `XCEditor`. App implementation files now include through
+  explicit module roots such as `app/Composition`, `app/Features`,
+  `app/Windowing`, `app/Rendering`, `app/Scene`, `app/Services`,
+  `app/Support`, `app/Bootstrap`, and `app/Platform/Win32`.
 
 The root issue is not the existence of a single executable target by itself.
 The root issue was that shared app contracts were stored inside concrete layer
 directories, and CMake exposed the whole `editor/app` include root through
 `XCEditorCore` usage requirements. The public include surface has now been
-narrowed; remaining work is to remove internal source compatibility with the
-private app root and finish wiring app-core tests against the narrowed surface.
+narrowed, and internal source compatibility with the private app root has now
+been removed. Remaining work is to finish wiring app-core tests against the
+narrowed surface and continue converging host code on the target directory
+shape.
 
 ## Target Directory Shape
 
@@ -402,9 +410,10 @@ Completed cuts:
 - Neutral host-facing contracts now live under `app/Host/Interfaces/`.
 - `EditorWindowTransferRequests`, window screen geometry, and title-bar chrome
   metrics now live under `app/Core/Windowing/`.
-- `XCEditorCore` now keeps `editor/app` as a private implementation include
-  root while exposing only `app/Core`, `app/Commands`, `app/State`, and
-  `app/Host` through its public usage requirements.
+- `XCEditorCore` now exposes only `app/Core`, `app/Commands`, `app/State`, and
+  `app/Host` through its public usage requirements, and both `XCEditorCore`
+  and `XCEditor` enumerate explicit private module roots instead of using
+  `editor/app` as a compatibility include directory.
 - Remaining work in this phase is to continue converging concrete host code on
   the `app/Host/Win32` and `app/Host/D3D12` directory shape.