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>

tests-ui/tests/litegraph/core/LGraph.test.ts

@@ -1,6 +1,6 @@
 import { describe } from 'vitest'
 
-import { LGraph, LiteGraph } from '@/lib/litegraph/src/litegraph'
+import { LGraph, LGraphNode, LiteGraph } from '@/lib/litegraph/src/litegraph'
 
 import { test } from './fixtures/testExtensions'
 
@@ -128,6 +128,54 @@ describe('Floating Links / Reroutes', () => {
   })
 })
 
+describe('Graph Clearing and Callbacks', () => {
+  test('clear() calls both node.onRemoved() and graph.onNodeRemoved()', ({
+    expect
+  }) => {
+    const graph = new LGraph()
+
+    // Create test nodes with onRemoved callbacks
+    const node1 = new LGraphNode('TestNode1')
+    const node2 = new LGraphNode('TestNode2')
+
+    // Add nodes to graph
+    graph.add(node1)
+    graph.add(node2)
+
+    // Track callback invocations
+    const nodeRemovedCallbacks = new Set<string>()
+    const graphRemovedCallbacks = new Set<string>()
+
+    // Set up node.onRemoved() callbacks
+    node1.onRemoved = () => {
+      nodeRemovedCallbacks.add(String(node1.id))
+    }
+    node2.onRemoved = () => {
+      nodeRemovedCallbacks.add(String(node2.id))
+    }
+
+    // Set up graph.onNodeRemoved() callback
+    graph.onNodeRemoved = (node) => {
+      graphRemovedCallbacks.add(String(node.id))
+    }
+
+    // Verify nodes are in graph before clearing
+    expect(graph.nodes.length).toBe(2)
+
+    // Clear the graph
+    graph.clear()
+
+    // Verify both types of callbacks were called
+    expect(nodeRemovedCallbacks).toContain(String(node1.id))
+    expect(nodeRemovedCallbacks).toContain(String(node2.id))
+    expect(graphRemovedCallbacks).toContain(String(node1.id))
+    expect(graphRemovedCallbacks).toContain(String(node2.id))
+
+    // Verify nodes were actually removed
+    expect(graph.nodes.length).toBe(0)
+  })
+})
+
 describe('Legacy LGraph Compatibility Layer', () => {
   test('can be extended via prototype', ({ expect, minimalGraph }) => {
     // @ts-expect-error Should always be an error.