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/components/common/TreeExplorerV2.vue

@@ -1,37 +1,41 @@
 <template>
   <ContextMenuRoot>
-    <TreeRoot
-      :expanded="[...expandedKeys]"
-      :items="root.children ?? []"
-      :get-key="(item) => item.key"
-      :get-children="
-        (item) => (item.children?.length ? item.children : undefined)
-      "
-      class="m-0 p-0 pb-6"
-    >
-      <TreeVirtualizer
-        v-slot="{ item }"
-        :estimate-size="36"
-        :text-content="(item) => item.value.label ?? ''"
+    <ContextMenuTrigger :disabled="!showContextMenu" as-child>
+      <TreeRoot
+        :expanded="[...expandedKeys]"
+        :items="root.children ?? []"
+        :get-key="(item) => item.key"
+        :get-children="
+          (item) => (item.children?.length ? item.children : undefined)
+        "
+        class="m-0 p-0 pb-6"
       >
-        <TreeExplorerV2Node
-          :item="
-            item as FlattenedItem<RenderedTreeExplorerNode<ComfyNodeDefImpl>>
-          "
-          @node-click="
-            (node: RenderedTreeExplorerNode<ComfyNodeDefImpl>, e: MouseEvent) =>
-              emit('nodeClick', node, e)
-          "
+        <TreeVirtualizer
+          v-slot="{ item }"
+          :estimate-size="36"
+          :text-content="(item) => item.value.label ?? ''"
         >
-          <template #folder="{ node }">
-            <slot name="folder" :node="node" />
-          </template>
-          <template #node="{ node }">
-            <slot name="node" :node="node" />
-          </template>
-        </TreeExplorerV2Node>
-      </TreeVirtualizer>
-    </TreeRoot>
+          <TreeExplorerV2Node
+            :item="
+              item as FlattenedItem<RenderedTreeExplorerNode<ComfyNodeDefImpl>>
+            "
+            @node-click="
+              (
+                node: RenderedTreeExplorerNode<ComfyNodeDefImpl>,
+                e: MouseEvent
+              ) => emit('nodeClick', node, e)
+            "
+          >
+            <template #folder="{ node }">
+              <slot name="folder" :node="node" />
+            </template>
+            <template #node="{ node }">
+              <slot name="node" :node="node" />
+            </template>
+          </TreeExplorerV2Node>
+        </TreeVirtualizer>
+      </TreeRoot>
+    </ContextMenuTrigger>
 
     <ContextMenuPortal v-if="showContextMenu">
       <ContextMenuContent
@@ -49,7 +53,11 @@
             "
             class="size-4"
           />
-          {{ $t('sideToolbar.nodeLibraryTab.sections.favorites') }}
+          {{
+            isCurrentNodeBookmarked
+              ? $t('sideToolbar.nodeLibraryTab.sections.unfavoriteNode')
+              : $t('sideToolbar.nodeLibraryTab.sections.favoriteNode')
+          }}
         </ContextMenuItem>
       </ContextMenuContent>
     </ContextMenuPortal>
@@ -63,6 +71,7 @@ import {
   ContextMenuItem,
   ContextMenuPortal,
   ContextMenuRoot,
+  ContextMenuTrigger,
   TreeRoot,
   TreeVirtualizer
 } from 'reka-ui'