Refactor spline system to use IPS_Editor_SplineEditable interface:
- New interface in Spline/PS_Editor_SplineEditable.h with all editing methods
- APS_Editor_SplineActor and APS_BehaviorEditor_AISpline both implement it
- All ~40 Cast<APS_Editor_SplineActor> replaced with Cast<IPS_Editor_SplineEditable>
- UndoManager SplinePointAction uses TWeakObjectPtr<AActor> + interface cast
- Any actor implementing the interface works with full editor spline editing
Spline visibility:
- SetVisualizationVisible() hides tube/handles/cube in gameplay (data stays for AI)
- SceneLoader calls it when stripping editor components
- SplineMatOccluded material added (unused for now, PP occlusion planned)
Other improvements:
- Snap spline CP to ground on placement (downward raytrace)
- Play button works without BaseLevel (uses current editor map)
- AISpline triggers SplineNetwork::RebuildNetwork on BeginPlay (next tick)
- PS_BehaviorEditor marked EnabledByDefault: false (only active in PROSERVE)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>