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/registry/types.ts

@@ -1,5 +1,5 @@
 import type { ComponentType } from 'react'
-import type { BufferGeometry, Object3D } from 'three'
+import type { BufferGeometry, Object3D, Ray } from 'three'
 import type { ZodObject, z } from 'zod'
 import type { MaterialSchema } from '../schema/material'
 import type { SceneMaterial, SceneMaterialId } from '../schema/scene-material'
@@ -1212,6 +1212,14 @@ export type PaintResolveArgs = {
   hitObjectName?: string
   /** Optional: the three.js object that received the pointer hit. Items read userData.slotId off it. */
   hitObject?: Object3D
+  /**
+   * Optional: the pointer's world ray, so a kind can re-raycast its OWN subtree
+   * to pick the precise sub-mesh under the cursor — independent of what the
+   * shared scene raycast hit first. Door/window use this: their opening proxy
+   * (a proud invisible cutout) wins the scene raycast over the wall in front of
+   * the recessed door body, then they re-raycast their parts to find the slot.
+   */
+  ray?: Ray
 }
 
 export type PaintPatchArgs = {