fix(fig): omit populated instance children on export

- Match Figma files where INSTANCE node changes carry symbol refs, not child nodes
- Prevent exported roundtrips from expanding every populated instance subtree
- Tighten glyph blob preservation now that instance children are omitted

packages/core/src/kiwi/node-change/export-node.ts

@@ -279,7 +279,10 @@ export function sceneNodeToKiwiWithContext(
   }
 
   const result: KiwiNodeChange[] = [nc]
-  const children = context.graph.getChildren(node.id).filter((child) => !child.internalOnly)
+  const children =
+    node.type === 'INSTANCE'
+      ? []
+      : context.graph.getChildren(node.id).filter((child) => !child.internalOnly)
   for (let i = 0; i < children.length; i++) {
     result.push(...context.sceneNodeToKiwi(children[i], guid, i, localIdCounter, context))
   }

tests/engine/io/fig/roundtrip/glyph-blob.test.ts

@@ -56,9 +56,8 @@ describe('roundtrip: text glyph blobs', () => {
     const output = countGlyphBlobs(exported)
 
     expect(input.glyphsWithBlob).toBeGreaterThan(0)
-    expect(output.glyphsWithBlob).toBeGreaterThan(0)
-    expect(output.uniqueGlyphBlobs).toBeLessThan(output.glyphsWithBlob / 100)
-    expect(output.uniqueGlyphBlobs).toBeLessThanOrEqual(input.uniqueGlyphBlobs + 20)
+    expect(output.glyphsWithBlob).toBe(input.glyphsWithBlob)
+    expect(output.uniqueGlyphBlobs).toBeLessThanOrEqual(input.uniqueGlyphBlobs)
   })
 
   test('deduplicates generated glyph blobs across repeated text', async () => {

tests/engine/io/subgraph.test.ts

@@ -56,7 +56,7 @@ describe('export subgraph extraction', () => {
     expect(extracted.graph.getNode(libraryPage.id)?.type).toBe('CANVAS')
   })
 
-  test('fig page export preserves valid instance component references', async () => {
+  test('fig page export preserves valid instance component references without serializing instance children', async () => {
     await initCodec()
     const graph = new SceneGraph()
     const page = graph.getPages()[0]
@@ -79,5 +79,12 @@ describe('export subgraph extraction', () => {
     expect(parsedInstance?.type).toBe('INSTANCE')
     expect(parsedInstance?.componentId).toBeTruthy()
     expect(parsed.getNode(parsedInstance?.componentId ?? '')?.type).toBe('COMPONENT')
+
+    const exportedAgain = await exportFigFile(extracted.graph)
+    const reparsed = await parseFigFile(exportedAgain.buffer as ArrayBuffer)
+    const reparsedInstance = [...reparsed.getAllNodes()].find(
+      (node) => node.type === 'INSTANCE' && node.name === instance.name
+    )
+    expect(reparsedInstance?.childIds).toEqual([])
   })
 })