Add UI core node lifetime handles

docs/modernization/build-inventory.md

@@ -733,6 +733,11 @@ powershell -ExecutionPolicy Bypass -File scripts\automation\apple-remote-build.p
   and platform triplet migration. Root CMake target
   `panopainter_platform_build_vcpkg_ui_core` focuses that gate on the
   vcpkg-backed `pp_ui_core`/tinyxml2 boundary and `pp_ui_core_layout_xml_tests`.
+- `pp_ui_core` now owns a pure `NodeLifetimeTree` target model with checked
+  node handles, hidden parent/child invariants, scoped callback connections,
+  mutation-safe event dispatch, and focused destroy-during-callback coverage in
+  `pp_ui_core_node_lifetime_tests`. Retained `Node` still needs to adopt those
+  semantics under DEBT-0063.
 - `scripts/automation/analyze.*` runs shader validation plus a
   renderer-boundary guard that reports JSON and fails if active non-backend
   source code reintroduces raw `GL_*`/`WGL_*` constants outside the allowed
@@ -1248,8 +1253,9 @@ Known warnings after the current CMake app build:
   `ShaderManager::ext_*` fields directly.
 - `pp_legacy_ui_core` is an object-library containment boundary because the
   retained base `Node` controls still depend on legacy renderer and app
-  headers. It should shrink as layout parsing, colors, generic controls, and
-  text/image primitives move to `pp_ui_core`.
+  headers. It should shrink as layout parsing, colors, generic controls,
+  tested node lifetime handles/connections, and text/image primitives move to
+  `pp_ui_core`.
 - `pp_panopainter_ui` currently surfaces existing legacy `Node`/`Serializer`
   header and static-analysis warnings while it still depends on
   `pp_legacy_app`; these should be reduced as the UI core/app UI boundary is