fix: resolve ImageCrop input image through subgraph nodes (#8899)

## Summary
When ImageCrop's input comes from a subgraph node, getInputNode returns
the subgraph node itself which has no image outputs.
Use resolveSubgraphOutputLink to trace through to the actual source node
(e.g. LoadImage) inside the subgraph.

Use canvas.graph (the currently active graph/subgraph) as the primary
lookup, falling back to rootGraph. When the ImageCrop node is inside a
subgraph, rootGraph cannot find it since it only contains root-level
nodes.

## Screenshots (if applicable)
before


https://github.com/user-attachments/assets/c3995f7c-6bcd-41fe-bc41-cfd87f9be94a


after


https://github.com/user-attachments/assets/ac660f58-6e6a-46ad-a441-84c7b88d28e2

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8899-fix-resolve-ImageCrop-input-image-through-subgraph-nodes-3086d73d36508172a759d7747190591f)
by [Unito](https://www.unito.io)

src/composables/useImageCrop.ts

@@ -155,11 +155,18 @@ export function useImageCrop(nodeId: NodeId, options: UseImageCropOptions) {
   const getInputImageUrl = (): string | null => {
     if (!node.value) return null
 
-    const inputNode = node.value.getInputNode(0)
+    let sourceNode = node.value.getInputNode(0)
+    if (!sourceNode) return null
 
-    if (!inputNode) return null
+    if (sourceNode.isSubgraphNode()) {
+      const link = node.value.getInputLink(0)
+      if (!link) return null
+      const resolved = sourceNode.resolveSubgraphOutputLink(link.origin_slot)
+      sourceNode = resolved?.outputNode ?? null
+      if (!sourceNode) return null
+    }
 
-    const urls = nodeOutputStore.getNodeImageUrls(inputNode)
+    const urls = nodeOutputStore.getNodeImageUrls(sourceNode)
 
     if (urls?.length) {
       return urls[0]
@@ -562,7 +569,10 @@ export function useImageCrop(nodeId: NodeId, options: UseImageCropOptions) {
 
   const initialize = () => {
     if (nodeId != null) {
-      node.value = app.rootGraph?.getNodeById(nodeId) || null
+      node.value =
+        app.canvas?.graph?.getNodeById(nodeId) ||
+        app.rootGraph?.getNodeById(nodeId) ||
+        null
     }
 
     updateImageUrl()