Import exported documents with durable root and reference remapping

src/lib/canvas-runtime/import-native.ts

@@ -27,7 +27,7 @@ export function prepareNativeImport(line:ImportLine,job:ImportJob,reserve:(key:s
   const record=clone(raw.record) as Record<string,Json>;if(record.id!==raw.key)throw fault('import_source_identity_mismatch');
   const dependencies=new Set<string>(),elementIds=new Map<Id,Id>(),canvasIds=new Map<Id,Id>();
   const element=(id:Json):Id=>{if(typeof id!=='string'||!id)throw fault('invalid_import_reference');const key=`element:${id}`;dependencies.add(key);const mapped=reserve(key);elementIds.set(id,mapped);return mapped;};
-  const owner=(id:Json):Id=>{if(id==='$target'){canvasIds.set('$target',source.targetCanvasId);return source.targetCanvasId;}if(typeof id!=='string'||!id)throw fault('invalid_import_reference');const key=`canvas:${id}`;dependencies.add(key);const mapped=reserve(key);canvasIds.set(id,mapped);return mapped;};
+  const owner=(id:Json):Id=>{if(id==='$target'||source.kind==='native-document'&&id===raw.sourceRootId){canvasIds.set(id as string,source.targetCanvasId);return source.targetCanvasId;}if(typeof id!=='string'||!id)throw fault('invalid_import_reference');const key=`canvas:${id}`;dependencies.add(key);const mapped=reserve(key);canvasIds.set(id,mapped);return mapped;};
   const key=`${raw.kind}:${raw.key}`,id=reserve(key);
   if(raw.kind==='canvas'){
     const parent=record.parent as Record<string,Json>|null;
@@ -37,6 +37,7 @@ export function prepareNativeImport(line:ImportLine,job:ImportJob,reserve:(key:s
   }
   const original=record as unknown as ElementRecord,definition=registry.components.get(original.componentId);
   if(registry.resolve(original)!=='known'||!definition?.copy||!original.data||typeof original.data!=='object'||Array.isArray(original.data))throw fault('import_component_unavailable');
+  if(source.kind==='native-document'&&definition.resourceFields?.some(key=>original.data[key]!==undefined&&original.data[key]!==null))throw fault('import_resource_authorization_required');
   for(const ref of definition.copy.references)for(const item of copyReferenceIds(original.data,ref)){if(ref.target==='element')element(item);else owner(item);}
   const after={...record,id,incarnation:1,ownerCanvasId:owner(original.ownerCanvasId),data:remapCopyData(original,registry,elementIds,canvasIds,document)};
   if(original.structure==='connection'){