[test] Add component test for image compare widget (#5549)

## Summary

Added comprehensive component test suite for WidgetImageCompare widget
with 410 test assertions covering display, edge cases, and integration
scenarios.

## Changes

- **What**: Created [Vue Test Utils](https://vue-test-utils.vuejs.org/)
test suite for [WidgetImageCompare
component](src/renderer/extensions/vueNodes/widgets/components/WidgetImageCompare.vue)
using [Vitest](https://vitest.dev/) testing framework

## Review Focus

Test coverage completeness for string vs object value handling,
accessibility attribute propagation, and edge case robustness including
malformed URLs and empty states.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5549-test-Add-component-test-for-image-compare-widget-26e6d73d365081189fe0d010f87d1eec)
by [Unito](https://www.unito.io)

---------

Co-authored-by: DrJKL <DrJKL@users.noreply.github.com>

src/renderer/extensions/vueNodes/widgets/components/WidgetImageCompare.vue

@@ -30,7 +30,7 @@ import { computed } from 'vue'
 
 import type { SimplifiedWidget } from '@/types/simplifiedWidget'
 
-interface ImageCompareValue {
+export interface ImageCompareValue {
   before: string
   after: string
   beforeAlt?: string