fix: add delete/bookmark actions for blueprints in V2 node library sidebar (#10827)

## Summary

Add missing delete and bookmark actions for user blueprints in the V2
node library sidebar, fixing parity with the V1 sidebar.

## Changes

- **What**: 
- Add delete button (inline + context menu) for user blueprints in
`TreeExplorerV2Node` and `TreeExplorerV2`
- Extract `isUserBlueprint()` helper in `subgraphStore` for DRY usage
across V1/V2 sidebars


![Kapture 2026-04-03 at 00 12
09](https://github.com/user-attachments/assets/3f1f3f41-ed2b-4250-953f-511d39e54e45)

## Review Focus

- `isUserBlueprint` consolidates logic previously duplicated between
`NodeTreeLeaf` and the new V2 components
- Context menu guard `contextMenuNode?.data` prevents showing empty
menus
- Folder `@contextmenu` handler clears stale `contextMenuNode` to
prevent wrong actions

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10827-fix-add-delete-bookmark-actions-for-blueprints-in-V2-node-library-sidebar-3366d73d36508111afd2c2c7d8ff0220)
by [Unito](https://www.unito.io)

src/components/common/TreeExplorerV2Node.test.ts

@@ -13,7 +13,7 @@ import TreeExplorerV2Node from './TreeExplorerV2Node.vue'
 const i18n = createI18n({
   legacy: false,
   locale: 'en',
-  messages: { en: {} }
+  messages: { en: { g: { delete: 'Delete' } } }
 })
 
 vi.mock('@/platform/settings/settingStore', () => ({
@@ -29,6 +29,17 @@ vi.mock('@/stores/nodeBookmarkStore', () => ({
   })
 }))
 
+const mockDeleteBlueprint = vi.fn()
+const mockIsUserBlueprint = vi.fn().mockReturnValue(false)
+
+vi.mock('@/stores/subgraphStore', () => ({
+  useSubgraphStore: () => ({
+    isUserBlueprint: mockIsUserBlueprint,
+    deleteBlueprint: mockDeleteBlueprint,
+    typePrefix: 'SubgraphBlueprint.'
+  })
+}))
+
 vi.mock('@/components/node/NodePreviewCard.vue', () => ({
   default: { template: '<div />' }
 }))
@@ -175,8 +186,12 @@ describe('TreeExplorerV2Node', () => {
       expect(contextMenuNode.value).toEqual(nodeItem.value)
     })
 
-    it('does not set contextMenuNode for folder items', async () => {
-      const contextMenuNode = ref<RenderedTreeExplorerNode | null>(null)
+    it('clears contextMenuNode when right-clicking a folder', async () => {
+      const contextMenuNode = ref<RenderedTreeExplorerNode | null>({
+        key: 'stale',
+        type: 'node',
+        label: 'Stale'
+      } as RenderedTreeExplorerNode)
 
       const { wrapper } = mountComponent(
         { item: createMockItem('folder') },
@@ -194,6 +209,59 @@ describe('TreeExplorerV2Node', () => {
     })
   })
 
+  describe('blueprint actions', () => {
+    beforeEach(() => {
+      vi.clearAllMocks()
+    })
+
+    it('shows delete button for user blueprints', () => {
+      mockIsUserBlueprint.mockReturnValue(true)
+      const { wrapper } = mountComponent({
+        item: createMockItem('node', {
+          data: { name: 'SubgraphBlueprint.test' }
+        })
+      })
+
+      expect(wrapper.find('[aria-label="Delete"]').exists()).toBe(true)
+    })
+
+    it('hides delete button for non-blueprint nodes', () => {
+      mockIsUserBlueprint.mockReturnValue(false)
+      const { wrapper } = mountComponent({
+        item: createMockItem('node', {
+          data: { name: 'KSampler' }
+        })
+      })
+
+      expect(wrapper.find('[aria-label="Delete"]').exists()).toBe(false)
+    })
+
+    it('always shows bookmark button', () => {
+      mockIsUserBlueprint.mockReturnValue(true)
+      const { wrapper } = mountComponent({
+        item: createMockItem('node', {
+          data: { name: 'SubgraphBlueprint.test' }
+        })
+      })
+
+      expect(wrapper.find('[aria-label="icon.bookmark"]').exists()).toBe(true)
+    })
+
+    it('calls deleteBlueprint when delete button is clicked', async () => {
+      mockIsUserBlueprint.mockReturnValue(true)
+      const nodeName = 'SubgraphBlueprint.test'
+      const { wrapper } = mountComponent({
+        item: createMockItem('node', {
+          data: { name: nodeName }
+        })
+      })
+
+      await wrapper.find('[aria-label="Delete"]').trigger('click')
+
+      expect(mockDeleteBlueprint).toHaveBeenCalledWith(nodeName)
+    })
+  })
+
   describe('rendering', () => {
     it('renders node icon for node type', () => {
       const { wrapper } = mountComponent({