refactor(app): choose split group sizes at the call site

packages/app/src/components/split-container.tsx

@@ -872,19 +872,6 @@ function SplitGroupChild({
   );
 }
 
-/**
- * Sizes from a divider drag are kept per group id, apart from the layout tree. A group keeps its
- * id when panes are added or removed, so the dragged sizes only apply while they still have one
- * entry per child; otherwise the dividers past the end of the list could not move.
- */
-function resolveGroupSizes(
-  layoutSizes: number[],
-  draggedSizes: number[] | undefined,
-  childCount: number,
-): number[] {
-  return draggedSizes?.length === childCount ? draggedSizes : layoutSizes;
-}
-
 /**
  * Flex grow per child, renormalized so the visible ones always sum to 1.
  *
@@ -981,11 +968,12 @@ function SplitNodeView({
     groupId ? state.splitSizesByWorkspace[workspaceKey]?.[groupId] : undefined,
   );
   const groupChildren = node.kind === "group" ? node.group.children : EMPTY_SPLIT_NODES;
-  const groupSizes = resolveGroupSizes(
-    node.kind === "group" ? node.group.sizes : EMPTY_SPLIT_SIZES,
-    storedGroupSizes,
-    groupChildren.length,
-  );
+  // Dragged sizes live per group id, apart from the layout tree, and a group keeps its id when
+  // panes are added or removed. They only apply while they still have one entry per child;
+  // otherwise the dividers past the end of the list could not move.
+  const layoutGroupSizes = node.kind === "group" ? node.group.sizes : EMPTY_SPLIT_SIZES;
+  const groupSizes =
+    storedGroupSizes?.length === groupChildren.length ? storedGroupSizes : layoutGroupSizes;
   const visibleFlex = useMemo(
     () => resolveVisibleGroupFlex(groupChildren, groupSizes, maximizedPaneId),
     [groupChildren, groupSizes, maximizedPaneId],