feat(paint-slots): per-part paint for windows + doors, chrome/brass, world-scale UVs

Builds on the explicit per-mesh slot tagging (currentDoorSlot/currentWindowSlot):

- Per-part painting: door = panel/frame/glass/hardware, window = frame/glass,
  each independently paintable. The recessed door/window body sits behind the
  wall, so the proud invisible cutout wins the scene raycast over the wall and
  the shared resolveSlotByReRaycast() re-raycasts the kind's own subtree to pick
  the exact part under the cursor (panel↔frame↔glass↔hardware). Hover tracks the
  cursor via a  re-eval (idempotent, no flicker).
- Door frame is its own slot (separate frameMaterial); hardware = new flat
  'metal-chrome'.
- Library defaults (generic): panel/frame -> library:preset-softwhite, glass ->
  library:preset-glass (flipped preset-glass to FrontSide — DoubleSide poisons
  the WebGPU MRT pass; it's the only glass we use).
- Catalog: add flat (non-PBR) 'metal-chrome' + 'metal-brass'; drop metal
  metalness 1 -> 0.6 so metals are lit by existing lights (no env needed).
- World-scale UVs (1 unit = 1m) on door/window box meshes via shared box-uv.ts,
  so finishes tile at real-world scale instead of stretching.
- PaintResolveArgs gains an optional  for subtree re-raycasting.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/core/src/material-library.ts

@@ -3442,7 +3442,9 @@ export const MATERIAL_CATALOG: MaterialCatalogItem[] = [
         bumpScale: 1,
         emissiveColor: '#000000',
         aoMapIntensity: 1,
-        side: 2,
+        // FrontSide — DoubleSide on a NodeMaterial poisons the WebGPU MRT scene
+        // pass (window/door glass relies on this). It's the only glass we use.
+        side: 0,
         opacity: 0.3,
         lightMapIntensity: 1,
       },
@@ -3953,7 +3955,7 @@ export const MATERIAL_CATALOG: MaterialCatalogItem[] = [
       mapProperties: {
         color: '#ffffff',
         roughness: 0.4,
-        metalness: 1,
+        metalness: 0.6,
         repeatX: 1,
         repeatY: 1,
         rotation: 0,
@@ -3992,7 +3994,7 @@ export const MATERIAL_CATALOG: MaterialCatalogItem[] = [
       mapProperties: {
         color: '#ffffff',
         roughness: 0.3,
-        metalness: 1,
+        metalness: 0.6,
         repeatX: 1,
         repeatY: 1,
         rotation: 0,
@@ -4033,7 +4035,77 @@ export const MATERIAL_CATALOG: MaterialCatalogItem[] = [
       mapProperties: {
         color: '#ffffff',
         roughness: 0.45,
-        metalness: 1,
+        metalness: 0.6,
+        repeatX: 1,
+        repeatY: 1,
+        rotation: 0,
+        wrapS: 'Repeat',
+        wrapT: 'Repeat',
+        normalScaleX: 1,
+        normalScaleY: 1,
+        emissiveIntensity: 1,
+        displacementScale: 0,
+        transparent: false,
+        flipY: false,
+        bumpScale: 1,
+        emissiveColor: '#000000',
+        aoMapIntensity: 1,
+        side: 0,
+        opacity: 1,
+        lightMapIntensity: 1,
+      },
+    },
+  },
+  {
+    // Parameter-only metal (no texture maps) — a worked example of a non-PBR
+    // catalog finish driven purely by three.js material settings.
+    id: 'metal-brass',
+    label: 'Brass',
+    category: 'metal',
+    surfaces: ['furniture', 'wall'],
+    description: 'Polished brass (flat metal, no maps)',
+    previewColor: '#b08d57',
+    preset: {
+      maps: {},
+      mapProperties: {
+        color: '#b08d57',
+        roughness: 0.35,
+        metalness: 0.9,
+        repeatX: 1,
+        repeatY: 1,
+        rotation: 0,
+        wrapS: 'Repeat',
+        wrapT: 'Repeat',
+        normalScaleX: 1,
+        normalScaleY: 1,
+        emissiveIntensity: 1,
+        displacementScale: 0,
+        transparent: false,
+        flipY: false,
+        bumpScale: 1,
+        emissiveColor: '#000000',
+        aoMapIntensity: 1,
+        side: 0,
+        opacity: 1,
+        lightMapIntensity: 1,
+      },
+    },
+  },
+  {
+    // Parameter-only chrome (no texture maps) — moderate metalness so it reads
+    // as bright metal under direct/ambient light without needing an env map.
+    id: 'metal-chrome',
+    label: 'Chrome',
+    category: 'metal',
+    surfaces: ['furniture', 'wall'],
+    description: 'Polished chrome (flat metal, no maps)',
+    previewColor: '#c8ccce',
+    preset: {
+      maps: {},
+      mapProperties: {
+        color: '#c8ccce',
+        roughness: 0.2,
+        metalness: 0.6,
         repeatX: 1,
         repeatY: 1,
         rotation: 0,