Formalize scene viewport navigation input helpers

docs/plan/SceneViewport_Overlay_Gizmo_Rework_Checkpoint_2026-04-02.md

@@ -1,5 +1,28 @@
 # SceneViewport Overlay/Gizmo Rework Checkpoint
 
+## Update 2026-04-04 Phase 5E
+
+### Navigation/Input State Formalization Completed
+
+- Added `SceneViewportEditorModes.h` to move shared scene viewport editor mode enums out of `SceneViewPanel.h`.
+- Added `SceneViewportNavigation.h` as the formal navigation/input helper layer for:
+  - tool shortcut resolution
+  - look/pan drag state transitions
+  - mouse/keyboard capture requests
+  - `SceneViewportInput` assembly
+  - interaction-resolution gating
+- `SceneViewPanel` now owns one `SceneViewportNavigationState` instead of multiple raw drag booleans and no longer assembles scene viewport input inline.
+- Removed the dead `m_loggedLookDelta` / `m_loggedPanDelta` panel state that no longer influenced runtime behavior.
+- Added focused editor tests for shortcut mapping, drag transitions, capture flags, input assembly, and interaction gating.
+
+### Verification
+
+- `cmake --build build --config Debug --target editor_tests -- /p:BuildProjectReferences=false`
+- `build/tests/Editor/Debug/editor_tests.exe --gtest_filter=SceneViewportNavigationTest.*:SceneViewportInteractionActionsTest.*:SceneViewportInteractionResolverTest.*:SceneViewportTransformGizmoCoordinatorTest.*:SceneViewportOverlayRenderer_Test.*:SceneViewportOverlayProviderRegistryTest.*:ViewportRenderFlowUtilsTest.*`
+- `cmake --build build --config Debug --target XCEditor`
+
+All commands completed successfully in `Debug`.
+
 ## Update 2026-04-04 Phase 5D
 
 ### Stage-Oriented Gizmo Frame API Completed