[refactor] Extract executionErrorStore from executionStore (#9060)

## Summary
Extracts error-related state and logic from `executionStore` into a
dedicated `executionErrorStore` for better separation of concerns.

## Changes
- **New store**: `executionErrorStore` with all error state
(`lastNodeErrors`, `lastExecutionError`, `lastPromptError`), computed
properties (`hasAnyError`, `totalErrorCount`,
`activeGraphErrorNodeIds`), and UI state (`isErrorOverlayOpen`,
`showErrorOverlay`, `dismissErrorOverlay`)
- **Moved util**: `executionIdToNodeLocatorId` extracted to
`graphTraversalUtil`, reusing `traverseSubgraphPath` and accepting
`rootGraph` as parameter
- **Updated consumers**: 12 files updated to import from
`executionErrorStore`
- **Backward compat**: Deprecated getters retained in `ComfyApp` for
extension compatibility

## Review Focus
- Deprecated getters in `app.ts` — can be removed in a future
breaking-change PR once extension authors migrate

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9060-refactor-Extract-executionErrorStore-from-executionStore-30e6d73d36508101973de835ab6b199f)
by [Unito](https://www.unito.io)

src/stores/executionStore.test.ts

@@ -2,6 +2,8 @@ import { setActivePinia } from 'pinia'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 import { app } from '@/scripts/app'
 import { useExecutionStore } from '@/stores/executionStore'
+import { useExecutionErrorStore } from '@/stores/executionErrorStore'
+import { executionIdToNodeLocatorId } from '@/utils/graphTraversalUtil'
 
 // Create mock functions that will be shared
 const mockNodeExecutionIdToNodeLocatorId = vi.fn()
@@ -80,20 +82,20 @@ describe('useExecutionStore - NodeLocatorId conversions', () => {
       // Mock app.rootGraph.getNodeById to return the mock node
       vi.mocked(app.rootGraph.getNodeById).mockReturnValue(mockNode)
 
-      const result = store.executionIdToNodeLocatorId('123:456')
+      const result = executionIdToNodeLocatorId(app.rootGraph, '123:456')
 
       expect(result).toBe('a1b2c3d4-e5f6-7890-abcd-ef1234567890:456')
     })
 
     it('should convert simple node ID to NodeLocatorId', () => {
-      const result = store.executionIdToNodeLocatorId('123')
+      const result = executionIdToNodeLocatorId(app.rootGraph, '123')
 
       // For simple node IDs, it should return the ID as-is
       expect(result).toBe('123')
     })
 
     it('should handle numeric node IDs', () => {
-      const result = store.executionIdToNodeLocatorId(123)
+      const result = executionIdToNodeLocatorId(app.rootGraph, 123)
 
       // For numeric IDs, it should convert to string and return as-is
       expect(result).toBe('123')
@@ -103,7 +105,9 @@ describe('useExecutionStore - NodeLocatorId conversions', () => {
       // Mock app.rootGraph.getNodeById to return null (node not found)
       vi.mocked(app.rootGraph.getNodeById).mockReturnValue(null)
 
-      expect(store.executionIdToNodeLocatorId('999:456')).toBe(undefined)
+      expect(executionIdToNodeLocatorId(app.rootGraph, '999:456')).toBe(
+        undefined
+      )
     })
   })
 
@@ -174,13 +178,13 @@ describe('useExecutionStore - reconcileInitializingJobs', () => {
   })
 })
 
-describe('useExecutionStore - Node Error Lookups', () => {
-  let store: ReturnType<typeof useExecutionStore>
+describe('useExecutionErrorStore - Node Error Lookups', () => {
+  let store: ReturnType<typeof useExecutionErrorStore>
 
   beforeEach(() => {
     vi.clearAllMocks()
     setActivePinia(createTestingPinia({ stubActions: false }))
-    store = useExecutionStore()
+    store = useExecutionErrorStore()
   })
 
   describe('getNodeErrors', () => {