test: Add test to prevent regression of workflow corruption during graph loading (#10623)

## Summary

Adds regression test for
https://github.com/Comfy-Org/ComfyUI_frontend/pull/9531

## Changes

- **What**:  
- registers extension that triggers checkState during
afterConfigureGraph (at this point the workflow data and active graph
are not in sync), previously causing it to overwrite the workflow data
- switches between tabs
- ensures they are not corrupted

Line 35 can be uncommented to cause the test to fail by clearing the
isLoadingGraph flag

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10623-test-Add-test-to-prevent-regression-of-workflow-corruption-during-graph-loading-3306d73d3650815fbf02ef23dfdcddce)
by [Unito](https://www.unito.io)

browser_tests/tests/changeTrackerLoadGuard.spec.ts

@@ -0,0 +1,66 @@
+import {
+  comfyExpect as expect,
+  comfyPageFixture as test
+} from '../fixtures/ComfyPage'
+import type { WorkspaceStore } from '../types/globals'
+
+test.describe(
+  'Change Tracker - isLoadingGraph guard',
+  { tag: '@workflow' },
+  () => {
+    test.beforeEach(async ({ comfyPage }) => {
+      await comfyPage.workflow.setupWorkflowsDirectory({})
+    })
+
+    test('Prevents checkState from corrupting workflow state during tab switch', async ({
+      comfyPage
+    }) => {
+      // Tab 0: default workflow (7 nodes)
+      expect(await comfyPage.nodeOps.getGraphNodesCount()).toBe(7)
+
+      // Save tab 0 so it has a unique name for tab switching
+      await comfyPage.menu.topbar.saveWorkflow('workflow-a')
+
+      // Register an extension that forces checkState during graph loading.
+      // This simulates the bug scenario where a user clicks during graph loading
+      // which triggers a checkState call on the wrong graph, corrupting the activeState.
+      await comfyPage.page.evaluate(() => {
+        window.app!.registerExtension({
+          name: 'TestCheckStateDuringLoad',
+          afterConfigureGraph() {
+            const workflow = (window.app!.extensionManager as WorkspaceStore)
+              .workflow.activeWorkflow
+            if (!workflow) throw new Error('No workflow found')
+            // Bypass the guard to reproduce the corruption bug:
+            // ; (workflow.changeTracker.constructor as unknown as { isLoadingGraph: boolean }).isLoadingGraph = false
+
+            // Simulate the user clicking during graph loading
+            workflow.changeTracker.checkState()
+          }
+        })
+      })
+
+      // Create tab 1: blank workflow (0 nodes)
+      await comfyPage.menu.topbar.triggerTopbarCommand(['New'])
+      await comfyPage.nextFrame()
+      expect(await comfyPage.nodeOps.getGraphNodesCount()).toBe(0)
+
+      // Switch back to tab 0 (workflow-a).
+      const tab0 = comfyPage.menu.topbar.getWorkflowTab('workflow-a')
+      await tab0.click()
+      await comfyPage.nextFrame()
+      expect(await comfyPage.nodeOps.getGraphNodesCount()).toBe(7)
+
+      // switch to blank tab and back to verify no corruption
+      const tab1 = comfyPage.menu.topbar.getWorkflowTab('Unsaved Workflow')
+      await tab1.click()
+      await comfyPage.nextFrame()
+      expect(await comfyPage.nodeOps.getGraphNodesCount()).toBe(0)
+
+      // switch again and verify no corruption
+      await tab0.click()
+      await comfyPage.nextFrame()
+      expect(await comfyPage.nodeOps.getGraphNodesCount()).toBe(7)
+    })
+  }
+)