sync: update core and viewer from monorepo (#143)

Major changes:
- Roof system rewrite with roof-segment support
- Scene store refactor
- Spatial grid improvements
- Item light system
- Post-processing and selection manager updates
- Perf monitor component

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/core/src/index.ts

@@ -11,6 +11,7 @@ export type {
   LevelEvent,
   NodeEvent,
   RoofEvent,
+  RoofSegmentEvent,
   SiteEvent,
   SlabEvent,
   WallEvent,
@@ -46,7 +47,7 @@ export {
   type ItemInteractiveState,
   useInteractive,
 } from './store/use-interactive'
-export { default as useScene } from './store/use-scene'
+export { clearSceneHistory, default as useScene } from './store/use-scene'
 // Systems
 export { CeilingSystem } from './systems/ceiling/ceiling-system'
 export { DoorSystem } from './systems/door/door-system'