feat(sidebar): autofocus search input in Workflows, Model, and Node tabs (#7179)

## Summary
This PR improves the user experience by automatically focusing the
search input field when opening the Workflows, Model Library, or Node
Library sidebar tabs.

## Changes
- **SearchBox.vue**: Exposed a `focus()` method to allow parent
components to programmatically set focus on the input.
- **WorkflowsSidebarTab.vue**: Added a watcher to focus the search box
when the tab is activated.
- **ModelLibrarySidebarTab.vue**: Added autofocus on component mount.
- **NodeLibrarySidebarTab.vue**: Added autofocus on component mount.

## Motivation
Users often switch to these tabs specifically to search for an item.
Automatically focusing the search box reduces friction and saves a
click.



https://github.com/user-attachments/assets/8438e71c-a5e4-4b6c-8665-04d535d3ad8e

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7179-feat-sidebar-autofocus-search-input-in-Workflows-Model-and-Node-tabs-2c06d73d36508199b8c0e83d19f1cd84)
by [Unito](https://www.unito.io)

src/components/sidebar/tabs/ModelLibrarySidebarTab.vue

@@ -21,6 +21,7 @@
     </template>
     <template #header>
       <SearchBox
+        ref="searchBoxRef"
         v-model:model-value="searchQuery"
         class="model-lib-search-box p-2 2xl:p-4"
         :placeholder="$t('g.searchModels') + '...'"
@@ -66,6 +67,7 @@ import { buildTree } from '@/utils/treeUtil'
 const modelStore = useModelStore()
 const modelToNodeStore = useModelToNodeStore()
 const settingStore = useSettingStore()
+const searchBoxRef = ref()
 const searchQuery = ref<string>('')
 const expandedKeys = ref<Record<string, boolean>>({})
 const { expandNode, toggleNodeOnEvent } = useTreeExpansion(expandedKeys)
@@ -180,6 +182,7 @@ watch(
 )
 
 onMounted(async () => {
+  searchBoxRef.value?.focus()
   if (settingStore.get('Comfy.ModelLibrary.AutoLoadAll')) {
     await modelStore.loadModels()
   }