Fix item surface placement and remove item height annotations

packages/core/src/hooks/spatial-grid/spatial-grid-manager.ts

@@ -1,5 +1,5 @@
 import type { AnyNode, CeilingNode, ItemNode, SlabNode, WallNode } from '../../schema'
-import { getScaledDimensions } from '../../schema'
+import { getScaledDimensions, isLowProfileItemSurface } from '../../schema'
 import useScene from '../../store/use-scene'
 import { SpatialGrid } from './spatial-grid'
 import { WallSpatialGrid } from './wall-spatial-grid'
@@ -582,6 +582,7 @@ export class SpatialGridManager {
       if (node.type !== 'item') continue
       const item = node as ItemNode
       if (item.asset.attachTo) continue
+      if (isLowProfileItemSurface(item)) continue
       if (ignoreSet.has(item.id)) continue
       if (resolveNodeLevelId(item, nodes) !== levelId) continue
 

packages/core/src/schema/index.ts

@@ -55,7 +55,12 @@ export type {
   TemperatureControl,
   ToggleControl,
 } from './nodes/item'
-export { getScaledDimensions, ItemNode } from './nodes/item'
+export {
+  getScaledDimensions,
+  ItemNode,
+  isLowProfileItemSurface,
+  LOW_PROFILE_ITEM_SURFACE_MAX_HEIGHT,
+} from './nodes/item'
 export { LevelNode } from './nodes/level'
 export type { RoofSurfaceMaterialRole, RoofSurfaceMaterialSpec } from './nodes/roof'
 export { getEffectiveRoofSurfaceMaterial, RoofNode } from './nodes/roof'

packages/core/src/schema/nodes/item.ts

@@ -135,6 +135,20 @@ export const ItemNode = BaseNode.extend({
 
 export type ItemNode = z.infer<typeof ItemNode>
 
+export const LOW_PROFILE_ITEM_SURFACE_MAX_HEIGHT = 0.1
+
+/**
+ * Low, floor-resting items like rugs and parking mats can receive items visually,
+ * but should not become item parents or block normal floor placement.
+ */
+export function isLowProfileItemSurface(item: ItemNode): boolean {
+  if (item.asset.attachTo) return false
+  const surfaceHeight = item.asset.surface
+    ? item.asset.surface.height * item.scale[1]
+    : getScaledDimensions(item)[1]
+  return surfaceHeight <= LOW_PROFILE_ITEM_SURFACE_MAX_HEIGHT
+}
+
 /**
  * Returns the effective world-space dimensions of an item after applying its scale.
  * Use this everywhere item.asset.dimensions is used for spatial calculations.