fix: WebGPU renderer race on Canvas remount & duplicate item scale loss (#284)

Backport from monorepo PR #310 (fix/april-pass):

1. WebGPU renderer race on Canvas remount
   Cache the in-flight WebGPURenderer promise per canvas element so
   concurrent configure() calls from R3F's useLayoutEffect await the
   same init() instead of creating duplicate renderers. Fixes
   intermittent 'resolve target size does not match' errors when
   navigating between projects and home.

2. Duplicate item loses its scale
   Add scale to the field set in useDraftNode.commit() so duplicated
   items preserve their original scale instead of falling back to
   [1,1,1].

Co-authored-by: Pascal <open@pascal.app>

packages/editor/src/components/tools/item/use-draft-node.ts

@@ -130,6 +130,7 @@ export function useDraftNode(): DraftNodeHandle {
       useScene.getState().updateNode(draft.id, {
         position: updateProps.position ?? draft.position,
         rotation: updateProps.rotation ?? draft.rotation,
+        scale: updateProps.scale ?? draft.scale,
         side: updateProps.side ?? draft.side,
         metadata: updateProps.metadata ?? stripTransient(draft.metadata),
         parentId: parentId as string,
@@ -161,6 +162,7 @@ export function useDraftNode(): DraftNodeHandle {
       asset: draft.asset,
       position: updateProps.position ?? draft.position,
       rotation: updateProps.rotation ?? draft.rotation,
+      scale: updateProps.scale ?? draft.scale,
       side: updateProps.side ?? draft.side,
       metadata: updateProps.metadata ?? stripTransient(draft.metadata),
     })