Chore: Upgrade Vitest to v4 (#7797)

## Summary

https://vitest.dev/guide/migration.html#vitest-4

## Changes

- **What**: Update Vitest and some associated dependencies
- **What**: Fix issue with our existing mocks and mock types

## Review Focus

Double check the test updates. I tried to keep the changes minimal.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7797-Chore-Upgrade-Vitest-to-v4-2d96d73d3650810cbe3ac42d7bd6585a)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

tests-ui/tests/composables/useLoad3d.test.ts

@@ -117,7 +117,9 @@ describe('useLoad3d', () => {
       }
     }
 
-    vi.mocked(Load3d).mockImplementation(() => mockLoad3d)
+    vi.mocked(Load3d).mockImplementation(function () {
+      Object.assign(this, mockLoad3d)
+    })
 
     mockToastStore = {
       addAlert: vi.fn()
@@ -289,7 +291,7 @@ describe('useLoad3d', () => {
     })
 
     it('should handle initialization errors', async () => {
-      vi.mocked(Load3d).mockImplementationOnce(() => {
+      vi.mocked(Load3d).mockImplementationOnce(function () {
         throw new Error('Load3d creation failed')
       })