feat: add material system for all node types

- Add MaterialSchema with 10 presets (white, brick, concrete, wood, glass, metal, plaster, tile, marble, custom)
- Add material field to Wall, Slab, Door, Window, Ceiling, Roof, RoofSegment nodes
- Create MaterialPicker UI component with preset selection and custom properties
- Update all renderers to support material rendering with caching
- Add Material section to all node panels (WallPanel, SlabPanel, DoorPanel, WindowPanel, CeilingPanel, RoofPanel, RoofSegmentPanel)
- Update AGENTS.md with Material System documentation

packages/viewer/src/components/renderers/wall/wall-renderer.tsx

@@ -1,7 +1,8 @@
 import { useRegistry, useScene, type WallNode } from '@pascal-app/core'
-import { useLayoutEffect, useRef } from 'react'
+import { useLayoutEffect, useMemo, useRef } from 'react'
 import type { Mesh } from 'three'
 import { useNodeEvents } from '../../../hooks/use-node-events'
+import { createMaterial, DEFAULT_WALL_MATERIAL } from '../../../lib/materials'
 import { NodeRenderer } from '../node-renderer'
 
 export const WallRenderer = ({ node }: { node: WallNode }) => {
@@ -9,18 +10,19 @@ export const WallRenderer = ({ node }: { node: WallNode }) => {
 
   useRegistry(node.id, 'wall', ref)
 
-  // Mark dirty on mount so WallSystem rebuilds geometry when wall (re)appears
   useLayoutEffect(() => {
     useScene.getState().markDirty(node.id)
   }, [node.id])
 
   const handlers = useNodeEvents(node, 'wall')
 
+  const material = useMemo(() => {
+    return node.material ? createMaterial(node.material) : DEFAULT_WALL_MATERIAL
+  }, [node.material])
+
   return (
-    <mesh castShadow receiveShadow ref={ref} visible={node.visible}>
-      {/* WallSystem will replace this geometry in the next frame */}
+    <mesh castShadow receiveShadow ref={ref} visible={node.visible} material={material}>
       <boxGeometry args={[0, 0, 0]} />
-      {/* Collision mesh: full-wall geometry (no cutouts) for pointer events */}
       <mesh name="collision-mesh" visible={false} {...handlers}>
         <boxGeometry args={[0, 0, 0]} />
       </mesh>