fix: onNodeRemoved not called when loading new graph (and tearing down previous) (#5407)

* standardize graph cleanup

* test: fix useCoreCommands tests and add regression test

- Fix mocking to properly simulate app.clean() calling graph.clear()
- Add intelligent subgraph detection in mock to match real implementation
- Add regression test for Vue node cleanup bug to prevent future regressions
- Ensures app.clean() properly triggers onNodeRemoved events through graph.clear()

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* fix unit tests

* move beforeLoadNewGraph to before graph is cleaned

---------

Co-authored-by: Claude <noreply@anthropic.com>

src/scripts/app.ts

@@ -1058,6 +1058,8 @@ export class ComfyApp {
       checkForRerouteMigration = false
     } = {}
   ) {
+    useWorkflowService().beforeLoadNewGraph()
+
     if (clean !== false) {
       this.clean()
     }
@@ -1093,7 +1095,6 @@ export class ComfyApp {
         severity: 'warn'
       })
     }
-    useWorkflowService().beforeLoadNewGraph()
     useSubgraphService().loadSubgraphs(graphData)
 
     const missingNodeTypes: MissingNodeType[] = []
@@ -1765,6 +1766,12 @@ export class ComfyApp {
     executionStore.lastExecutionError = null
 
     useDomWidgetStore().clear()
+
+    // Subgraph does not properly implement `clear` and the parent class's
+    // (`LGraph`) `clear` breaks the subgraph structure.
+    if (this.graph && !this.canvas.subgraph) {
+      this.graph.clear()
+    }
   }
 
   clientPosToCanvasPos(pos: Vector2): Vector2 {

src/scripts/ui.ts

@@ -634,7 +634,6 @@ export class ComfyUI {
               confirm('Clear workflow?')
             ) {
               app.clean()
-              app.graph.clear()
               useLitegraphService().resetView()
               api.dispatchCustomEvent('graphCleared')
             }