Tighten XCUI schema consistency rules

docs/plan/XCUI_Phase_Status_2026-04-05.md

@@ -74,7 +74,7 @@ Current gap:
 - `XCNewEditor` Debug target builds successfully
 - `core_ui_tests`: `14/14`
 - `core_ui_style_tests`: `5/5`
-- `ui_resource_tests`: `7/7`
+- `ui_resource_tests`: `11/11`
 - `editor_tests` targeted bridge smoke: `3/3`
 
 ## Landed This Phase
@@ -94,6 +94,10 @@ Current gap:
   - artifact schema version bump for UI documents
   - loader/resource accessors and memory accounting
   - schema compile/load/artifact regression coverage
+  - schema consistency rules for:
+    - `allowedValues` only on `enum`
+    - `documentKind` / `restrictDocumentKind` only on `document`
+    - explicit `documentKind` required when `restrictDocumentKind=true`
 - Engine runtime layer added:
   - `UIScreenPlayer`
   - `UIDocumentScreenHost`