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/utils/textTickerUtils.test.ts

@@ -0,0 +1,58 @@
+import { describe, expect, it } from 'vitest'
+
+import { splitTextAtWordBoundary } from '@/utils/textTickerUtils'
+
+describe('splitTextAtWordBoundary', () => {
+  it('returns full text when ratio >= 1 (fits in one line)', () => {
+    expect(splitTextAtWordBoundary('Load Checkpoint', 1)).toEqual([
+      'Load Checkpoint',
+      ''
+    ])
+    expect(splitTextAtWordBoundary('Load Checkpoint', 1.5)).toEqual([
+      'Load Checkpoint',
+      ''
+    ])
+  })
+
+  it('splits at last word boundary before estimated break', () => {
+    // "Load Checkpoint Loader" = 22 chars, ratio 0.5 → estimate at char 11
+    // lastIndexOf(' ', 11) → 15? No: "Load Checkpoint Loader"
+    //                                  0123456789...
+    // ' ' at index 4 and 15
+    // lastIndexOf(' ', 11) → 4
+    expect(splitTextAtWordBoundary('Load Checkpoint Loader', 0.5)).toEqual([
+      'Load',
+      'Checkpoint Loader'
+    ])
+  })
+
+  it('splits longer text proportionally', () => {
+    // ratio 0.7 → estimate at char 15
+    // lastIndexOf(' ', 15) → 15 (the space between "Checkpoint" and "Loader")
+    expect(splitTextAtWordBoundary('Load Checkpoint Loader', 0.7)).toEqual([
+      'Load Checkpoint',
+      'Loader'
+    ])
+  })
+
+  it('returns full text when no word boundary found', () => {
+    expect(splitTextAtWordBoundary('Superlongwordwithoutspaces', 0.5)).toEqual([
+      'Superlongwordwithoutspaces',
+      ''
+    ])
+  })
+
+  it('handles single word text', () => {
+    expect(splitTextAtWordBoundary('Checkpoint', 0.5)).toEqual([
+      'Checkpoint',
+      ''
+    ])
+  })
+
+  it('handles ratio near zero', () => {
+    expect(splitTextAtWordBoundary('Load Checkpoint Loader', 0.1)).toEqual([
+      'Load Checkpoint Loader',
+      ''
+    ])
+  })
+})

src/utils/textTickerUtils.ts

@@ -0,0 +1,10 @@
+export function splitTextAtWordBoundary(
+  text: string,
+  ratio: number
+): [string, string] {
+  if (ratio >= 1) return [text, '']
+  const estimate = Math.floor(text.length * ratio)
+  const breakIndex = text.lastIndexOf(' ', estimate)
+  if (breakIndex <= 0) return [text, '']
+  return [text.substring(0, breakIndex), text.substring(breakIndex + 1)]
+}