Add XCUI schema document regression coverage

docs/plan/XCUI_Phase_Status_2026-04-05.md

@@ -9,8 +9,11 @@ Old `editor` replacement is explicitly out of scope for this phase.
 
 - Phase 1 sandbox batch committed and pushed as `67a28bd` (`Add XCUI new editor sandbox phase 1`).
 - Phase 2 common/runtime batch committed and pushed as `ade5be3` (`Add XCUI runtime screen layer and demo textarea`).
-- Current work has moved into Phase 3: stabilize schema/validation and continue filling the remaining common/runtime/editor gaps instead of replacing the old editor.
-- The current stable editor-layer batch is centered on `LayoutLab` as the widget proving ground for tree/list/property-section style controls.
+- Phase 3 has now produced a stable mixed batch across common/runtime/editor:
+  - schema document definition data is now retained on `UIDocumentModel` and round-trips through the UI artifact path
+  - engine runtime coverage was tightened again around `UISystem` and concrete document-host rendering
+  - `LayoutLab` continues as the editor widget proving ground for tree/list/property-section style controls
+- Old `editor` replacement remains deferred; all active execution still stays inside XCUI shared code and `new_editor`.
 
 ## Three-Layer Status
 
@@ -18,6 +21,8 @@ Old `editor` replacement is explicitly out of scope for this phase.
 
 - `UI::DrawData`, input event types, focus routing, style/theme resolution are in active use.
 - `UIDocumentCompiler` is buildable again after repairing the duplicated schema helper regression introduced by overlapping schema work.
+- `UIDocumentModel` / `UIDocumentResource` now retain schema definition metadata explicitly, including memory accounting and `UISchema` accessors.
+- `.xcschema` round-trip coverage is now present through compile, loader, artifact write, and artifact read paths.
 - Build-system hardening for MSVC/PDB output paths has started in root CMake, `engine/CMakeLists.txt`, `new_editor/CMakeLists.txt`, and `tests/NewEditor/CMakeLists.txt`.
 - Shared engine-side XCUI runtime scaffolding is now present under `engine/include/XCEngine/UI/Runtime` and `engine/src/UI/Runtime`.
 - Shared engine-side `UIDocumentScreenHost` now compiles `.xcui` / `.xctheme` screen documents into a runtime-facing document host path instead of leaving all document ownership in `new_editor`.
@@ -25,7 +30,7 @@ Old `editor` replacement is explicitly out of scope for this phase.
 
 Current gap:
 
-- Schema/validation is not yet landed in a stable form.
+- Minimal schema self-definition support is landed, but schema-driven validation for `.xcui` / `.xctheme` instances is still not implemented.
 - Shared widget/runtime instantiation is still thin and mostly editor-side.
 - Common widget primitives are still incomplete: multiline text editing, tree/list virtualization, property-grid composition, and native image/source-rect level APIs.
 
@@ -35,6 +40,7 @@ Current gap:
 - The demo runtime has moved past single-line input: multiline `TextArea` behavior is now covered in the sandbox testbed.
 - Engine-side runtime ownership is no longer zero: `UIScreenPlayer`, `UIDocumentScreenHost`, and `UISystem` now define a shared runtime contract for loading a screen document, ticking it with input, and collecting `UI::UIDrawData`.
 - `UISystem` now supports layered screen composition semantics: stacked screen players, top-interactive input routing, and modal layers that block lower screens.
+- Runtime screen emission now also carries concrete button text in the shared document host path instead of silently dropping button labels.
 
 Current gap:
 
@@ -66,6 +72,7 @@ Current gap:
 - `XCNewEditor` Debug target builds successfully
 - `core_ui_tests`: `14/14`
 - `core_ui_style_tests`: `5/5`
+- `ui_resource_tests`: `7/7`
 
 ## Landed This Phase
 
@@ -74,11 +81,17 @@ Current gap:
 - Demo authored resources updated to exercise the input field.
 - LayoutLab `ScrollView` prototype with clipping and hover rejection outside clipped content.
 - LayoutLab editor-widget prototypes for tree/list/property-style sections with dedicated runtime coverage.
+- Schema document support extended with:
+  - retained `UISchemaDefinition` data on `UIDocumentModel`
+  - artifact schema version bump for UI documents
+  - loader/resource accessors and memory accounting
+  - schema compile/load/artifact regression coverage
 - Engine runtime layer added:
   - `UIScreenPlayer`
   - `UIDocumentScreenHost`
   - `UISystem`
   - layered screen composition and modal blocking semantics
+- Runtime document-host draw emission now preserves button labels for shared screen rendering.
 - RHI image path improvements:
   - clipped image UV adjustment
   - mirrored image UV preservation
@@ -91,7 +104,7 @@ Current gap:
 
 ## Phase Risks Still Open
 
-- Schema/validation still needs a clean minimal landing instead of the current partially merged state in `UIDocumentCompiler.cpp`.
+- Schema instance validation is still open beyond `.xcschema` self-definition and artifact round-trip coverage.
 - `ScrollView` is still authored/static; no wheel-driven scrolling or virtualization yet.
 - `Image` widgets still do not have source-rect/atlas-subregion level API in the high-level draw command model.
 - Editor shell still depends on ImGui as host chrome.
@@ -99,8 +112,11 @@ Current gap:
 
 ## Next Phase
 
-1. Cleanly stabilize schema/validation in `UIDocumentCompiler.cpp` and add targeted schema regression tests.
+1. Expand schema rules just one level further inside `UIDocumentCompiler.cpp`:
+   - `allowedValues` only for `Enum`
+   - `documentKind` / `restrictDocumentKind` only for `Document`
+   - `restrictDocumentKind=true` requires explicit `documentKind`
 2. Expand runtime/game-layer ownership from the current document host + layered `UISystem` into reusable menu/HUD stack patterns and engine runtime integration.
 3. Promote the current editor-facing widget prototypes out of authored `LayoutLab` content and into reusable XCUI widget/runtime modules, then continue with toolbar/menu and more native shell-owned chrome.
-4. Move more diagnostics and shell affordances into XCUI-owned editor-layer surfaces instead of only ImGui HUDs.
+4. Start the window-level compositor split in `new_editor` so the editor shell can run through `ImGuiHostCompositor` first and then grow a native XCUI compositor path on the same seam.
 5. Continue phased validation, commit, push, and plan refresh after each stable batch.