Clip children to rounded corners when clipsContent is true

clipsContent was always using clipRect (sharp corners), ignoring the
node's corner radius. Frames and instances with rounded corners now
use clipRRect, matching Figma's behavior where content is clipped to
the rounded shape.

Fixes avatar images appearing as squares inside circular containers.

packages/core/src/renderer/scene.ts

@@ -95,11 +95,13 @@ function renderChildren(
     node.type === 'FRAME' || node.type === 'COMPONENT' || node.type === 'INSTANCE'
   if (isClippableContainer && node.clipsContent && node.childIds.length > 0) {
     canvas.save()
-    canvas.clipRect(
-      r.ck.LTRBRect(0, 0, node.width, node.height),
-      r.ck.ClipOp.Intersect,
-      true
-    )
+    const hasRadius = node.cornerRadius > 0 || (node.independentCorners &&
+      (node.topLeftRadius > 0 || node.topRightRadius > 0 || node.bottomRightRadius > 0 || node.bottomLeftRadius > 0))
+    if (hasRadius) {
+      canvas.clipRRect(r.makeRRect(node), r.ck.ClipOp.Intersect, true)
+    } else {
+      canvas.clipRect(r.ck.LTRBRect(0, 0, node.width, node.height), r.ck.ClipOp.Intersect, true)
+    }
     for (const childId of node.childIds) {
       r.renderNode(canvas, graph, childId, overlays, absX, absY)
     }