feat: implement NodeLibrarySidebarTabV2 with Reka UI components (#8548)

## Summary

Implement a redesigned Node Library sidebar using Reka UI components
with virtualized tree rendering and improved UX.

## Changes

- **What**: 
  - Add three-tab structure (Essential, All, Custom) using Reka UI Tabs
- Implement TreeExplorerV2 with virtualized tree using
TreeRoot/TreeVirtualizer for performance
  - Add node hover preview with teleport to show NodePreview component
  - Implement context menu for toggling favorites on nodes
  - Add search functionality that auto-expands matching folders
- Create panel components: EssentialNodesPanel, AllNodesPanel,
CustomNodesPanel
  - Add 'Open Manager' button in CustomNodesPanel
  - Use custom icons: comfy--node for nodes, ph--folder-fill for folders
  - New node preview component: `NodePreviewCard`
  - Api node folder icon
  - Node drag preview

- **Feature Flag**: Enabled via URL parameter `?nodeRedesign=true`

## Review Focus

- TreeExplorerV2.vue uses `[...expandedKeys]` to prevent internal
mutation by Reka UI TreeRoot
- Context menu injection key is exported from TreeExplorerV2Node.vue and
imported by TreeExplorerV2.vue
- Hover preview uses teleport to
`#node-library-node-preview-container-v2`

## Screenshots (if applicable)

| Feature | Screenshot | 
|---|---|
| All nodes tab |<img width="323" height="761" alt="image"
src="https://github.com/user-attachments/assets/1976222b-83dc-4a1b-838a-2d49aedea3b8"
/>|
| Custom nodes tab | <img width="308" height="748" alt="image"
src="https://github.com/user-attachments/assets/2c23bffb-bdaa-4c6c-8cac-7610fb7f3fb7"
/>|
|Api nodes icon | <img width="299" height="523" alt="image"
src="https://github.com/user-attachments/assets/e9ca05b0-1143-44cf-b227-6462173c7cd0"
/>|
| node preview|<img width="499" height="544" alt="image"
src="https://github.com/user-attachments/assets/8961a7b4-77ae-4e57-99cf-62d9e4e17088"
/>|
| node drag preview | <img width="434" height="289" alt="image"
src="https://github.com/user-attachments/assets/b5838c90-65d4-4bee-b2b3-c41b57870da8"
/>|



Test by adding `?nodeRedesign=true` to the URL

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8548-WIP-feat-implement-NodeLibrarySidebarTabV2-with-Reka-UI-components-2fb6d73d36508134b7e0f75a2c9b976a)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: bymyself <cbyrne@comfy.org>

src/composables/usePerTabState.test.ts

@@ -0,0 +1,73 @@
+import { ref } from 'vue'
+import { describe, expect, it } from 'vitest'
+
+import { usePerTabState } from './usePerTabState'
+
+type TabId = 'a' | 'b' | 'c'
+
+describe('usePerTabState', () => {
+  function setup(initialTab: TabId = 'a') {
+    const selectedTab = ref<TabId>(initialTab)
+    const stateByTab = ref<Record<TabId, string[]>>({
+      a: [],
+      b: [],
+      c: []
+    })
+    const state = usePerTabState(selectedTab, stateByTab)
+    return { selectedTab, stateByTab, state }
+  }
+
+  it('should return state for the current tab', () => {
+    const { selectedTab, stateByTab, state } = setup()
+
+    stateByTab.value.a = ['key1', 'key2']
+    stateByTab.value.b = ['key3']
+
+    expect(state.value).toEqual(['key1', 'key2'])
+
+    selectedTab.value = 'b'
+    expect(state.value).toEqual(['key3'])
+  })
+
+  it('should set state only for the current tab', () => {
+    const { stateByTab, state } = setup()
+
+    state.value = ['new-key1', 'new-key2']
+
+    expect(stateByTab.value.a).toEqual(['new-key1', 'new-key2'])
+    expect(stateByTab.value.b).toEqual([])
+    expect(stateByTab.value.c).toEqual([])
+  })
+
+  it('should preserve state when switching tabs', () => {
+    const { selectedTab, stateByTab, state } = setup()
+
+    state.value = ['a-key']
+    selectedTab.value = 'b'
+    state.value = ['b-key']
+    selectedTab.value = 'c'
+    state.value = ['c-key']
+
+    expect(stateByTab.value.a).toEqual(['a-key'])
+    expect(stateByTab.value.b).toEqual(['b-key'])
+    expect(stateByTab.value.c).toEqual(['c-key'])
+
+    selectedTab.value = 'a'
+    expect(state.value).toEqual(['a-key'])
+  })
+
+  it('should not share state between tabs', () => {
+    const { selectedTab, state } = setup()
+
+    state.value = ['only-a']
+
+    selectedTab.value = 'b'
+    expect(state.value).toEqual([])
+
+    selectedTab.value = 'c'
+    expect(state.value).toEqual([])
+
+    selectedTab.value = 'a'
+    expect(state.value).toEqual(['only-a'])
+  })
+})

src/composables/usePerTabState.ts

@@ -0,0 +1,14 @@
+import type { Ref } from 'vue'
+import { computed } from 'vue'
+
+export function usePerTabState<K extends string, V>(
+  selectedTab: Ref<K>,
+  stateByTab: Ref<Record<K, V>>
+) {
+  return computed({
+    get: () => stateByTab.value[selectedTab.value],
+    set: (value) => {
+      stateByTab.value[selectedTab.value] = value
+    }
+  })
+}