feat(store, flow)!: Add apply changes handlers

* flow will not update changes unless a handler to apply changes is passed
* a default handler is available in the useVueFlow composable
* removeElements export removed

src/utils/edge.ts

@@ -136,8 +136,8 @@ export const groupEdgesByZLevel = (edges: GraphEdge[], nodes: GraphNode[]) => {
     const z = edge.z
       ? edge.z
       : Math.max(
-          nodes[nodeIds.indexOf(edge.source)].computedPosition.z || 0,
-          nodes[nodeIds.indexOf(edge.target)].computedPosition.z || 0,
+          nodes[nodeIds.indexOf(edge.source)]?.computedPosition.z || 0,
+          nodes[nodeIds.indexOf(edge.target)]?.computedPosition.z || 0,
         )
     if (tree[z]) {
       tree[z].push(edge)