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/store/use-viewer.ts

@@ -71,6 +71,9 @@ type ViewerState = {
   debugColors: boolean
   setDebugColors: (enabled: boolean) => void
 
+  walkthroughMode: boolean
+  setWalkthroughMode: (mode: boolean) => void
+
   cameraDragging: boolean
   setCameraDragging: (dragging: boolean) => void
 }
@@ -194,6 +197,9 @@ const useViewer = create<ViewerState>()(
       debugColors: false,
       setDebugColors: (enabled) => set({ debugColors: enabled }),
 
+      walkthroughMode: false,
+      setWalkthroughMode: (mode) => set({ walkthroughMode: mode }),
+
       cameraDragging: false,
       setCameraDragging: (dragging) => set({ cameraDragging: dragging }),
     }),