Refactor editor command state contracts into core

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

@@ -37,9 +37,9 @@ The app layer has a good directory vocabulary but enforcement is still
 incomplete:
 
 - `XCEditorCore` now limits its public app include surface to
-  `editor/app/Core`, `editor/app/Commands`, `editor/app/State`, and
-  `editor/app/Host/Interfaces`, and app/core sources now include through
-  explicit module roots instead of a private `editor/app` compatibility root.
+  `editor/app/Core` and `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`.
 - Native editor resources now cross the app-core boundary through a neutral
@@ -78,6 +78,10 @@ Completed boundary cuts:
   utility-window runtime contracts accept this service view instead of
   `EditorContext`, so concrete feature panels no longer depend on
   `Composition/EditorContext.h`.
+- Command routing and shared state contracts now live under
+  `editor/app/Core/Commands` and `editor/app/Core/State`. `XCEditorCore`,
+  `XCEditor`, and app-facing tests expose those contracts through the single
+  `editor/app/Core` include surface instead of separate command/state roots.
 - Win32 now hands render startup a neutral
   `Rendering::Host::EditorWindowRenderRuntimeSurface` value, and D3D12 no
   longer includes `Platform/Win32/**` editor surface headers to obtain `HWND`.
@@ -304,12 +308,10 @@ add_library(XCEditorCore STATIC ...)
 Initial contents:
 
 - `app/Core/**`
-- `app/Commands/**`
 - `app/Composition/**`
 - `app/Features/**`
 - `app/Project/**` or `app/Services/Project/**`
 - `app/Scene/**` or `app/Services/Scene/**`
-- `app/State/**`
 - `app/Core/UtilityWindows/**`
 - `app/Core/Windowing/**`
 - `app/Windowing/**` core files that do not require Win32 or D3D12
@@ -516,8 +518,8 @@ 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 exposes only `app/Core`, `app/Commands`, `app/State`, and
-  `app/Host/Interfaces` through its public usage requirements, and both
+- `XCEditorCore` now exposes only `app/Core` and `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