feat(paint-slots): add drei sunset environment as an editor viewer child

Inject an EditorEnvironment wrapper (drei prefiltered sunset HDRI at
environmentIntensity 0.6) as a child of the editor Viewer, not baked into
the Viewer component, so read-only/embed viewers stay lightweight. This
gives PBR metals their reflections and lifts lighting on vertical walls
that flat directional + hemisphere lights cannot.

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

packages/editor/src/components/editor-environment.tsx

@@ -0,0 +1,20 @@
+'use client'
+
+import { Environment } from '@react-three/drei'
+import { Suspense } from 'react'
+
+/**
+ * Scene IBL for the editor — drei's prefiltered environment map. Injected as a
+ * <Viewer> *child* (not baked into the Viewer component) so read-only / embed
+ * viewers don't pull the HDRI. This is what gives PBR metals their reflections
+ * and lifts the lighting on vertical surfaces (walls), which flat directional +
+ * hemisphere lights can't do alone. Intensity is dialled below the preset
+ * default so it complements the scene lights rather than washing them out.
+ */
+export function EditorEnvironment() {
+  return (
+    <Suspense fallback={null}>
+      <Environment preset="sunset" environmentIntensity={0.6} />
+    </Suspense>
+  )
+}

packages/editor/src/components/editor/index.tsx

@@ -21,6 +21,7 @@ import {
 } from '../../lib/scene'
 import { initSFXBus } from '../../lib/sfx-bus'
 import useEditor from '../../store/use-editor'
+import { EditorEnvironment } from '../editor-environment'
 import { CeilingSelectionAffordanceSystem } from '../systems/ceiling/ceiling-selection-affordance-system'
 import { CeilingSystem } from '../systems/ceiling/ceiling-system'
 import { RoofEditSystem } from '../systems/roof/roof-edit-system'
@@ -602,6 +603,7 @@ const ViewerSceneContent = memo(function ViewerSceneContent({
   const noEditing = isVersionPreviewMode || isFirstPersonMode || isStudioMode
   return (
     <>
+      <EditorEnvironment />
       {!(isFirstPersonMode || isStudioMode) && <SelectionManager />}
       {!noEditing && <BoxSelectTool />}
       {!noEditing && <NodeArrowHandles />}