Default new_editor to native XCUI shell host

docs/plan/XCUI_Phase_Status_2026-04-05.md

@@ -16,6 +16,12 @@ Old `editor` replacement is explicitly out of scope for this phase.
   - `LayoutLab` continues as the editor widget proving ground for tree/list/property-section style controls
   - the demo sandbox and editor bridge APIs were tightened again without touching the old editor replacement scope
   - `new_editor` now has an explicit two-step window compositor seam through `IWindowUICompositor` / `ImGuiWindowUICompositor`, layered on top of `IEditorHostCompositor` / `ImGuiHostCompositor`
+- The native-host follow-up is now landed in `new_editor`:
+  - `NativeWindowUICompositor` is now buildable alongside the legacy ImGui compositor
+  - `Application` now defaults to a native XCUI host path instead of creating the ImGui shell by default
+  - the native default path now drives `XCUIDemoRuntime` and `XCUILayoutLabRuntime` directly, composes their `UIDrawData`, and submits one swapchain packet through the native compositor
+  - the old ImGui shell path remains present as an explicit compatibility host instead of the default host
+  - `XCUIInputBridge.h` no longer drags `imgui.h` through the public XCUI input seam
 - Old `editor` replacement remains deferred; all active execution still stays inside XCUI shared code and `new_editor`.
 
 ## Three-Layer Status
@@ -93,14 +99,24 @@ Current gap:
 - `XCUIDemoRuntime` now bridges pointer activation, text-edit commands, and shortcut-triggered commands through a unified command path, and `DrainPendingCommandIds()` now preserves mixed pointer/text/shortcut ordering.
 - `new_editor` now also has a pure `XCUIShellChromeState` model covering panel visibility, hosted-preview mode, and shell-level view toggles without depending on ImGui, `Application`, or the old editor.
 - `XCUIShellChromeState` hosted-preview mode naming is now backend-neutral (`HostedPresenter` / `NativeOffscreen`) instead of encoding `ImGui` into the XCUI shell model.
+- `new_editor` now also has a concrete `NativeWindowUICompositor` path and native-focused compositor tests, so the window compositor seam is no longer ImGui-only.
+- `Application` now also has a native XCUI shell path that:
+  - becomes the default `new_editor` startup path
+  - lays out `XCUI Demo` and `Layout Lab` as native cards directly in the swapchain window
+  - routes shell shortcuts through the same command router without reading ImGui capture state in the default host path
+  - drives both sandbox runtimes directly from Win32/XCUI input snapshots instead of routing through ImGui panel hosts
+  - composes one native `UIDrawData` packet and submits it through `NativeWindowUICompositor`
+- `NativeXCUIPanelCanvasHost` now backs that direct shell path as an externally driven canvas/session host for native cards instead of assuming an ImGui child-window model.
+- `XCUIInputBridge.h` no longer includes `imgui.h`, so the public XCUI input bridge seam is now host-neutral at the header boundary.
 - `XCNewEditor` builds successfully to `build/new_editor/bin/Debug/XCNewEditor.exe`.
 
 Current gap:
 
-- The shell is still ImGui-hosted.
-- Hosted-preview compatibility presentation still depends on an ImGui-specific inline draw target binding when the native queued surface path is disabled.
-- The panel-canvas seam still only has an ImGui adapter today; a native panel/shell host still needs to replace it before the editor shell can stop depending on ImGui host chrome.
-- Editor-specialized widgets are still incomplete at the shared-module level: the authored prototypes exist, but virtualization, multi-selection/focus traversal, toolbar/menu chrome, and icon-atlas widgets are not yet extracted into reusable XCUI modules, and broader editor-host keybinding plus full shell-state adoption are still only partially integrated.
+- The default shell host is now native, but the legacy ImGui shell and panel path still exists as a compatibility host and is still compiled into `new_editor`.
+- Hosted-preview offscreen surface publication is still not wired for the native compositor path because descriptor-backed texture registration is still ImGui-host-centric today.
+- The native shell currently proves direct runtime composition, but its shell chrome is still a bespoke `Application`-side layout rather than a fully shared XCUI-authored editor shell document.
+- Editor-specialized widgets are still incomplete at the shared-module level: the authored prototypes exist, but virtualization, multi-selection/focus traversal, toolbar/menu chrome, menu interaction widgets, and icon-atlas widgets are not yet extracted into reusable XCUI modules.
+- Shared image support is still incomplete for full native hosted-preview parity: `UI::UIDrawData` still lacks explicit source-rect/UV-level image commands, so native surface-image composition cannot yet mirror the ImGui panel host path exactly.
 
 ## Validated This Phase
 
@@ -113,11 +129,13 @@ Current gap:
 - `new_editor_xcui_rhi_render_backend_tests`: `5/5`
 - `new_editor_xcui_hosted_preview_presenter_tests`: `20/20`
 - `new_editor_imgui_window_ui_compositor_tests`: `7/7`
+- `new_editor_native_window_ui_compositor_tests`: `5/5`
 - `new_editor_xcui_editor_command_router_tests`: `5/5`
 - `new_editor_application_shell_command_bindings_tests`: `6/6`
 - `new_editor_xcui_shell_chrome_state_tests`: `11/11`
 - `new_editor_xcui_panel_canvas_host_tests`: `4/4`
 - `new_editor_imgui_xcui_panel_canvas_host_tests`: `1/1`
+- `new_editor_native_xcui_panel_canvas_host_tests`: `4/4`
 - `new_editor_xcui_layout_lab_panel_tests`: `3/3`
 - `XCNewEditor` Debug target builds successfully
 - `core_ui_tests`: `52 total` (`50` passed, `2` skipped because `KeyCode::Delete` currently aliases `Backspace`)
@@ -212,6 +230,12 @@ Current gap:
 - `XCUIShellChromeState` now also exposes effective hosted-preview state helpers and shell view-toggle command-id helpers, so shell routing code no longer has to manually combine enablement and requested preview mode.
 - `XCUIShellChromeState` hosted-preview modes were renamed away from `LegacyImGui`, so XCUI shell state no longer treats ImGui as the generic fallback concept.
 - The panel-canvas seam now has dedicated null/imgui backend coverage, including explicit backend/capability reporting and a non-ImGui placeholder host path for future native shell adoption.
+- The native host follow-up is now present in `new_editor`:
+  - `NativeWindowUICompositor` provides a swapchain-native XCUI packet present path beside the legacy ImGui compositor
+  - `Application` now defaults to that native host path and directly composes `XCUI Demo` plus `Layout Lab` into one native shell frame
+  - `NativeXCUIPanelCanvasHost` now drives externally configured native card sessions for that shell path
+  - new native compositor/native canvas-host tests now cover the new host seam
+- `XCUIInputBridge.h` no longer includes `imgui.h`, so XCUI input translation is no longer coupled to ImGui at the public header boundary.
 - `SceneRuntime` layered XCUI routing now has dedicated regression coverage for:
   - top-interactive layer input ownership
   - blocking/modal layer suppression of lower layers