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/NodeLibrarySidebarTab.vue

@@ -78,6 +78,7 @@
       <template #header>
         <div>
           <SearchBox
+            ref="searchBoxRef"
             v-model:model-value="searchQuery"
             class="node-lib-search-box p-2 2xl:p-4"
             :placeholder="$t('g.searchNodes') + '...'"
@@ -130,7 +131,7 @@ import Button from 'primevue/button'
 import Divider from 'primevue/divider'
 import Popover from 'primevue/popover'
 import type { Ref } from 'vue'
-import { computed, h, nextTick, ref, render } from 'vue'
+import { computed, h, nextTick, onMounted, ref, render } from 'vue'
 
 import SearchBox from '@/components/common/SearchBox.vue'
 import type { SearchFilter } from '@/components/common/SearchFilterChip.vue'
@@ -171,6 +172,12 @@ const { expandNode, toggleNodeOnEvent } = useTreeExpansion(expandedKeys)
 const nodeBookmarkTreeExplorerRef = ref<InstanceType<
   typeof NodeBookmarkTreeExplorer
 > | null>(null)
+const searchBoxRef = ref()
+
+onMounted(() => {
+  searchBoxRef.value?.focus()
+})
+
 const searchFilter = ref<InstanceType<typeof Popover> | null>(null)
 const groupingPopover = ref<InstanceType<typeof Popover> | null>(null)
 const sortingPopover = ref<InstanceType<typeof Popover> | null>(null)