Refine editor host boundary

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

@@ -38,9 +38,10 @@ incomplete:
 
 - `XCEditorCore` now limits its public app include surface to
   `editor/app/Core`, `editor/app/Commands`, `editor/app/State`, and
-  `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.
+  `editor/app/Host/Interfaces`, and app/core sources now include through
+  explicit module roots instead of a private `editor/app` compatibility root.
+  Concrete host code has converged under `editor/app/Host/Win32` and
+  `editor/app/Host/D3D12`.
 - Feature panels no longer use `Composition/EditorContext.h` directly, and
   the first app-core test target now exercises `XCEditorCore` outside the
   executable host.
@@ -72,6 +73,8 @@ Completed boundary cuts:
   `editor/app/Host/Interfaces`, including editor window host interfaces,
   render-runtime contracts, texture/viewport host contracts, pointer-capture
   contracts, and system interaction service interfaces.
+- Concrete Win32 and D3D12 host implementations now live under
+  `editor/app/Host/Win32` and `editor/app/Host/D3D12`.
 - Shared window screen geometry, chrome metrics, and frame transfer requests
   now live under `editor/app/Core/Windowing`, and
   `XCEditorCore` no longer exports the whole `editor/app` root as a public
@@ -80,7 +83,8 @@ Completed boundary cuts:
   `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`.
+  `app/Support`, `app/Bootstrap`, `app/Host/Interfaces`, `app/Host/Win32`,
+  and `app/Host/D3D12`.
 - `editor_app_core_tests` now links `XCEditorCore` directly and uses explicit
   app module include roots. Its initial suite covers host command routing,
   project runtime, shell asset validation, project browser model, hierarchy
@@ -92,9 +96,8 @@ directories, and CMake exposed the whole `editor/app` include root through
 `XCEditorCore` usage requirements. The public include surface has now been
 narrowed, and internal source compatibility with the private app root has now
 been removed. The first app-core test target now exercises the narrowed
-surface. Remaining work is to continue converging host code on the target
-directory shape and to restore additional stale app feature/viewport tests
-without widening the include surface.
+surface. Remaining work is to restore additional stale app feature/viewport
+tests without widening the include surface.
 
 ## Target Directory Shape
 
@@ -276,8 +279,8 @@ Keep in `XCEditor` executable:
 - `app/main.cpp`
 - `app/Bootstrap/Application.*`
 - `app/Bootstrap/EditorApp.rc`
-- `app/Platform/Win32/**`
-- `app/Rendering/D3D12/**`
+- `app/Host/Win32/**`
+- `app/Host/D3D12/**`
 - any concrete host glue that includes `windows.h`
 
 `XCEditor` links `XCEditorCore`, `XCUIEditor`, and concrete platform/rendering
@@ -317,6 +320,7 @@ Remaining stale test references to fix or remove in later cuts:
 
 - `Ports/SystemInteractionPort.h`
 - `Rendering/Viewport/ViewportRenderTargetInternal.h`
+- `app/Platform/Win32/WindowManager/TabDragDropTarget.h`
 
 The test target is part of the architecture. If app core cannot be tested
 without starting the executable host, the boundary is not real.
@@ -418,11 +422,12 @@ Completed cuts:
 - `EditorWindowTransferRequests`, window screen geometry, and title-bar chrome
   metrics now live under `app/Core/Windowing/`.
 - `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.
+  `app/Host/Interfaces` through its public usage requirements, and both
+  `XCEditorCore` and `XCEditor` enumerate explicit module roots instead of
+  using `editor/app` as a compatibility include directory.
+- Concrete Win32 and D3D12 host implementations now live under
+  `app/Host/Win32` and `app/Host/D3D12`; `XCEditor` consumes those roots
+  privately, while `XCEditorCore` only sees `app/Host/Interfaces`.
 
 ## Phase 6: Documentation Update