Fix node header height for subgraphs (#6525)

Node headers are slightly too tall on subgraph nodes due to the height
of the "enter subgraph" button. This is fixed by explicitly setting the
height of the enter subgraph button.
<img width="991" height="171" alt="image"
src="https://github.com/user-attachments/assets/34d049a7-1dee-46c2-ab28-169c3f546347"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6525-Fix-node-header-height-for-subgraphs-29f6d73d3650810eaf95e7a6d107c2bd)
by [Unito](https://www.unito.io)

src/renderer/extensions/vueNodes/components/NodeHeader.vue

@@ -68,9 +68,9 @@
         <IconButton
           v-if="isSubgraphNode"
           v-tooltip.top="enterSubgraphTooltipConfig"
-          size="sm"
           type="transparent"
           data-testid="subgraph-enter-button"
+          class="size-5"
           @click.stop="handleEnterSubgraph"
           @dblclick.stop
         >