fix: tree explorer nodes not filling parent container width (#9964)

## Summary

Fix tree explorer nodes not filling the full width of the sidebar
container, causing text to overflow instead of truncating.

## Changes

- **What**: Add `min-w-0` to `TreeRoot` to allow flex shrinking within
sidebar. Add `w-full` and `min-w-0` to tree node rows so
absolutely-positioned virtualizer items fill the container width and
text truncates correctly.
<img width="365" height="749" alt="image"
src="https://github.com/user-attachments/assets/320910f3-52ad-4634-a935-6bd1a40aea7f"
/>


## Review Focus

The virtualizer renders each item with `position: absolute; left: 0` but
no explicit width, so rows would size to content rather than filling the
container. Adding `w-full` ensures rows stretch to 100% of the
virtualizer container, and `min-w-0` allows proper flex shrinking for
deep indentation levels.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9964-fix-tree-explorer-nodes-not-filling-parent-container-width-3246d73d36508138be38fdcac15ae4ef)
by [Unito](https://www.unito.io)

Co-authored-by: Amp <amp@ampcode.com>

src/components/common/TreeExplorerV2.vue

@@ -8,7 +8,7 @@
         :get-children="
           (item) => (item.children?.length ? item.children : undefined)
         "
-        class="m-0 p-0 pb-6"
+        class="m-0 min-w-0 p-0 pb-6"
       >
         <TreeVirtualizer
           v-slot="{ item }"

src/components/common/TreeExplorerV2Node.vue

@@ -105,7 +105,7 @@ defineOptions({
 })
 
 const ROW_CLASS =
-  'group/tree-node flex cursor-pointer select-none items-center gap-3 overflow-hidden py-2 outline-none hover:bg-comfy-input mx-2 rounded'
+  'group/tree-node flex w-full min-w-0 cursor-pointer select-none items-center gap-3 overflow-hidden py-2 outline-none hover:bg-comfy-input mx-2 rounded'
 
 const { item } = defineProps<{
   item: FlattenedItem<RenderedTreeExplorerNode<ComfyNodeDefImpl>>