sync: comprehensive monorepo → editor parity (2D/3D decoupling, UX polish, crash fixes)

Squash merge of 3 commits:
1. useLiveTransforms store for 2D/3D decoupling + floorplan overhaul + Sentry crash fixes
2. Comprehensive 59-file sync bringing editor to full monorepo parity (selection highlights, delete tool, furnish/zone modes, keyboard shortcuts, all panels)
3. Missing files fix (materials.ts, merged-outline-node.ts, type fix)

75 files changed, ~6K additions.

packages/viewer/src/index.ts

@@ -1,4 +1,5 @@
 export { default as Viewer } from './components/viewer'
+export { WalkthroughControls } from './components/viewer/walkthrough-controls'
 export { ASSETS_CDN_URL, resolveAssetUrl, resolveCdnUrl } from './lib/asset-url'
 export { SCENE_LAYER, ZONE_LAYER } from './lib/layers'
 export {
@@ -13,7 +14,7 @@ export {
   DEFAULT_WINDOW_MATERIAL,
   disposeMaterial,
 } from './lib/materials'
+export { mergedOutline } from './lib/merged-outline-node'
 export { default as useViewer } from './store/use-viewer'
-export { ExportSystem } from './systems/export/export-system'
 export { InteractiveSystem } from './systems/interactive/interactive-system'
 export { snapLevelsToTruePositions } from './systems/level/level-utils'