Clarify editor production target shape

editor/AGENTS.md

@@ -13,14 +13,18 @@ change.
 - `XCUIEditor` outputs `XCUIEditor.lib` and is the reusable, platform-neutral
   editor UI layer. It links
   against `XCEngine` and is covered mainly by `tests/UI/Editor/unit`.
+- The production editor target shape is fixed at two targets:
+  `XCUIEditor`, the reusable editor UI library, and `XCEditor`, the product
+  executable. Production sources under `editor/app/**` belong directly to the
+  `XCEditor` executable target.
 - `XCEditor` is built when `XCENGINE_BUILD_XCUI_EDITOR_APP=ON`; that mode
   requires `XCENGINE_ENABLE_RENDERING_EDITOR_SUPPORT=ON`. The executable target
   is named `XCEditor`, but its output name is `XCEngine`.
 - The app target owns Win32 hosting, D3D12 window rendering, project/scene
   runtime wiring, real editor panels, utility windows, and screenshots.
-- The app is intentionally packaged as one executable target. Do not restore
-  internal app split targets such as `XCUIEditorAppLib`, `XCUIEditorAppCore`,
-  or `XCUIEditorHost` unless the product architecture is explicitly changed.
+- The app is intentionally packaged as one executable target. App boundaries are
+  source-directory ownership inside `XCEditor`; the CMake target graph stays at
+  the two-target production shape above.
 - Keep the CMake target named `XCEditor` so it does not collide with the engine
   library target named `XCEngine`; keep the built executable output name as
   `XCEngine`.
@@ -251,15 +255,16 @@ inside pure shell/widget code.
   Shared manual-validation hosts should write captures under the active build
   directory.
 
-## Current Architecture Debt
+## Current Architecture Notes
 
-- `XCEditor` is the intentional single executable app target. App-layer
-  boundaries are maintained through directory ownership, namespaces, app/service
-  interfaces, focused reusable-layer tests, manual-validation hosts, and smoke
-  diagnostics, not through internal app static-library targets.
-- Legacy app-split CMake targets have been removed. Do not reference
-  `XCUIEditorAppLib`, `XCUIEditorAppCore`, or `XCUIEditorHost` in new build
-  logic or tests.
+- `XCEditor` is the intentional single executable app target. This is a fixed
+  production target shape, matching the repository's preference for coarse
+  product targets plus directory/module ownership. App-layer boundaries are
+  maintained through directory ownership, namespaces, app/service interfaces,
+  focused reusable-layer tests, manual-validation hosts, and smoke diagnostics.
+- Legacy app-split CMake targets are retired architecture history. Current
+  build logic and tests use the two production editor targets above:
+  `XCUIEditor` and `XCEditor`.
 - Existing source-tree capture history is present under some manual-validation
   scenarios, but new captures should go to the build output directory.
 - Runtime trace files are the main app smoke diagnostic. Avoid replacing