feat(paint-slots): round-2 feedback — fence 2 slots + UVs, roof defaults, stair body

- fence: split into two paint slots — panel (posts/base/infill, default charcoal)
  and rail (cap, default wood-finewood27) — as separate meshes with userData.slotId.
  Fix applyFenceUVs to continuous world-space 1 UV unit = 1 m (drop the per-part
  min origin that broke tiling across parts). New generateFenceSlotGeometries.
- roof: real catalog defaults for the segment surfaces via getRoofMaterialArray
  (the actual default path): wall/trim concrete-plate (matches walls), deck +
  soffit soft-white, shingle terracotta; textures-off role escape hatch kept.
  Align nodes getRoofMaterials no-parent fallback to match.
- stair: body slot default -> preset-lightgrey.
- (biome formatting normalization of the round-1 merged renderer files rides along.)

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

packages/nodes/src/fence/geometry.ts

@@ -5,30 +5,30 @@ import {
   createDefaultMaterial,
   createMaterial,
   createSurfaceRoleMaterial,
-  generateFenceGeometry,
+  generateFenceSlotGeometries,
   type RenderShading,
   resolveMaterialRef,
   resolveSlotDefaultMaterial,
 } from '@pascal-app/viewer'
 import { FrontSide, Group, type Material, Mesh, type Texture } from 'three'
 import type { FenceNode } from './schema'
-import { FENCE_SLOT_DEFAULT } from './slots'
+import { FENCE_PANEL_SLOT_DEFAULT, FENCE_RAIL_SLOT_DEFAULT, type FenceSlotId } from './slots'
 
 /**
- * Stage B builder for fence. Reuses the legacy `generateFenceGeometry`
- * (pure function from viewer that returns a merged BufferGeometry of
- * posts + base + top rail + curve spans) and wraps it in a Mesh-in-Group
- * shape the generic `<GeometrySystem>` expects.
+ * Stage B builder for fence. Splits the geometry into two paintable slots —
+ * `panel` (posts / base / infill) and `rail` (the cap rail) — each its own Mesh
+ * with a `userData.slotId` so the unified slot paint resolves and previews per
+ * part.
  *
- * Materials follow the unified slot model: the single `surface` slot resolves
- * `node.slots.surface` (a shared scene material or `library:` finish) → the
- * legacy inline `node.material` / `materialPreset` (pre-slot-model scenes) →
- * the declared slot default. Textures-off collapses to themed joinery.
+ * Per slot the material resolves: `node.slots[slotId]` (a shared scene material
+ * or `library:` finish) → the legacy inline `node.material` / `materialPreset`
+ * (pre-slot-model scenes, applied to both parts) → the declared slot default.
+ * Textures-off collapses both parts to the themed joinery role.
  *
- * Phase 6 cleanup moves the 280 lines of geometry math out of the
- * legacy `viewer/src/systems/fence/fence-system.tsx` into this folder
- * once the legacy system file is deleted. Until then `generateFenceGeometry`
- * is publicly re-exported from viewer.
+ * Phase 6 cleanup moves the geometry math out of the legacy
+ * `viewer/src/systems/fence/fence-system.tsx` into this folder once the legacy
+ * system file is deleted. Until then `generateFenceSlotGeometries` is publicly
+ * re-exported from viewer.
  */
 type FenceMaterial = Material & {
   alphaMap?: Texture | null
@@ -37,10 +37,16 @@ type FenceMaterial = Material & {
   transparent: boolean
 }
 
+const SLOT_DEFAULTS: Record<FenceSlotId, string> = {
+  panel: FENCE_PANEL_SLOT_DEFAULT,
+  rail: FENCE_RAIL_SLOT_DEFAULT,
+}
+
 const fenceMaterialCache = new Map<string, Material>()
 
-function getFenceMaterial(
+function getFenceSlotMaterial(
   node: FenceNode,
+  slotId: FenceSlotId,
   shading: RenderShading,
   textures: boolean,
   colorPreset: ColorPreset,
@@ -51,7 +57,7 @@ function getFenceMaterial(
     return createSurfaceRoleMaterial('joinery', colorPreset, FrontSide, sceneTheme)
   }
 
-  const slotRef = node.slots?.surface
+  const slotRef = node.slots?.[slotId]
   if (slotRef) {
     const resolved = resolveMaterialRef(slotRef, sceneMaterials, shading)
     if (resolved) return resolved
@@ -61,7 +67,7 @@ function getFenceMaterial(
     return getLegacyFenceMaterial(node, shading)
   }
 
-  return resolveSlotDefaultMaterial(FENCE_SLOT_DEFAULT, shading, 0.8)
+  return resolveSlotDefaultMaterial(SLOT_DEFAULTS[slotId], shading, 0.8)
 }
 
 function getLegacyFenceMaterial(node: FenceNode, shading: RenderShading): Material {
@@ -105,13 +111,26 @@ export function buildFenceGeometry(
   sceneTheme?: string,
 ): Group {
   const group = new Group()
-  const geometry = generateFenceGeometry(node)
-  const material = getFenceMaterial(node, shading, textures, colorPreset, sceneTheme, ctx?.materials)
-  const mesh = new Mesh(geometry, material)
-  mesh.castShadow = true
-  mesh.receiveShadow = true
-  mesh.userData.slotId = 'surface'
-  mesh.userData.surfaceRole = 'joinery'
-  group.add(mesh)
+  const geometries = generateFenceSlotGeometries(node)
+
+  for (const slotId of ['panel', 'rail'] as const) {
+    const geometry = geometries[slotId]
+    if (geometry.getAttribute('position') === undefined) continue
+    const material = getFenceSlotMaterial(
+      node,
+      slotId,
+      shading,
+      textures,
+      colorPreset,
+      sceneTheme,
+      ctx?.materials,
+    )
+    const mesh = new Mesh(geometry, material)
+    mesh.castShadow = true
+    mesh.receiveShadow = true
+    mesh.userData.slotId = slotId
+    group.add(mesh)
+  }
+
   return group
 }