Rename XCUI compatibility host surface away from ImGui

docs/plan/XCUI_Phase_Status_2026-04-05.md

@@ -46,6 +46,7 @@ Old `editor` replacement is explicitly out of scope for this phase.
   - `XCUIShellChromeState` no longer carries the legacy host demo-window toggle or command id on the generic shell-state surface
   - `Application.h` no longer exposes that legacy demo command through generic `ShellCommandIds`, `ShellCommandBindings`, or `RegisterShellViewCommands(...)`
   - the legacy demo window toggle now lives as a compatibility-only command inside `ApplicationLegacyImGui.cpp`
+  - generic `Application` host-mode/member naming is now also shifting from `LegacyImGui` toward `CompatibilityHost`, so the default shell surface does not have to encode ImGui into every host-facing method name
 - Old `editor` replacement remains deferred; all active execution still stays inside XCUI shared code and `new_editor`.
 
 ## Three-Layer Status

new_editor/src/Application.cpp

@@ -1132,7 +1132,7 @@ void Application::Frame() {
         return;
     }
 
-    FrameLegacyImGuiHost();
+    FrameCompatibilityHost();
 }
 
 } // namespace NewEditor

new_editor/src/Application.h

@@ -52,7 +52,7 @@ public:
     using ShellViewToggleState = ::XCEngine::Editor::XCUIBackend::XCUIShellViewToggleState;
     enum class WindowHostMode : std::uint8_t {
         NativeXCUI = 0,
-        LegacyImGui
+        CompatibilityHost
     };
 
     struct ShellCommandIds {
@@ -420,12 +420,12 @@ private:
         const ::XCEngine::Editor::XCUIBackend::XCUIInputBridgeFrameSnapshot& snapshot);
     bool IsNativeWindowHostEnabled() const;
     void InitializePanelsForActiveWindowHost();
-    void InitializeLegacyImGuiPanels();
-    void RenderLegacyImGuiUiFrame();
+    void InitializeCompatibilityHostPanels();
+    void RenderCompatibilityHostUiFrame();
     ::XCEngine::UI::UIDrawData BuildNativeShellDrawData(
         const ::XCEngine::Editor::XCUIBackend::XCUIInputBridgeFrameSnapshot& shellSnapshot,
         const ::XCEngine::Editor::XCUIBackend::XCUIInputBridgeFrameDelta& shellFrameDelta);
-    void FrameLegacyImGuiHost();
+    void FrameCompatibilityHost();
     void FrameNativeXCUIHost();
     void RenderShellChrome();
     void RenderHostedPreviewHud();

new_editor/src/ApplicationLegacyImGui.cpp

@@ -119,11 +119,11 @@ void Application::InitializePanelsForActiveWindowHost() {
         return;
     }
 
-    InitializeLegacyImGuiPanels();
+    InitializeCompatibilityHostPanels();
     ConfigureHostedPreviewPresenters();
 }
 
-void Application::InitializeLegacyImGuiPanels() {
+void Application::InitializeCompatibilityHostPanels() {
     m_demoPanel = std::make_unique<XCUIDemoPanel>(
         &m_xcuiInputSource,
         CreateHostedPreviewPresenter(IsNativeHostedPreviewEnabled(ShellPanelId::XCUIDemo)),
@@ -267,7 +267,7 @@ void Application::InitializeWindowCompositor() {
     }
 }
 
-void Application::FrameLegacyImGuiHost() {
+void Application::FrameCompatibilityHost() {
     Application::BeginHostedPreviewFrameLifecycle(
         m_hostedPreviewQueue,
         m_hostedPreviewSurfaceRegistry);
@@ -279,7 +279,7 @@ void Application::FrameLegacyImGuiHost() {
 
     m_windowCompositor->RenderFrame(
         kLegacyHostClearColor,
-        [this]() { RenderLegacyImGuiUiFrame(); },
+        [this]() { RenderCompatibilityHostUiFrame(); },
         [this](
             const ::XCEngine::Rendering::RenderContext& renderContext,
             const ::XCEngine::Rendering::RenderSurface& surface) {
@@ -323,7 +323,7 @@ void Application::FrameLegacyImGuiHost() {
     m_xcuiInputSource.ClearFrameTransients();
 }
 
-void Application::RenderLegacyImGuiUiFrame() {
+void Application::RenderCompatibilityHostUiFrame() {
     ::XCEngine::Editor::XCUIBackend::XCUIInputBridgeCaptureOptions options = {};
     options.timestampNanoseconds = MakeLegacyHostFrameTimestampNanoseconds();
     options.windowFocused = m_xcuiInputSource.IsWindowFocused();