test: migrate 132 test files from @vue/test-utils to @testing-library/vue (#10965)

## Summary

Migrate 132 test files from `@vue/test-utils` (VTU) to
`@testing-library/vue` (VTL) with `@testing-library/user-event`,
adopting user-centric behavioral testing patterns across the codebase.

## Changes

- **What**: Systematic migration of component/unit tests from VTU's
`mount`/`wrapper` API to VTL's `render`/`screen`/`userEvent` API across
132 files in `src/`
- **Breaking**: None — test-only changes, no production code affected

### Migration breakdown

| Batch | Files | Description |
|-------|-------|-------------|
| 1 | 19 | Simple render/assert tests |
| 2A | 16 | Interactive tests with user events |
| 2B-1 | 14 | Interactive tests (continued) |
| 2B-2 | 32 | Interactive tests (continued) |
| 3A–3E | 51 | Complex tests (stores, composables, heavy mocking) |
| Lint fix | 7 | `await` on `fireEvent` calls for `no-floating-promises`
|
| Review fixes | 15 | Address CodeRabbit feedback (3 rounds) |

### Review feedback addressed

- Removed class-based assertions (`text-ellipsis`, `pr-3`, `.pi-save`,
`.skeleton`, `.bg-black\/15`, Tailwind utilities) in favor of
behavioral/accessible queries
- Added null guards before `querySelector` casts
- Added `expect(roots).toHaveLength(N)` guards before indexed NodeList
access
- Wrapped fake timer tests in `try/finally` for guaranteed cleanup
- Split double-render tests into focused single-render tests
- Replaced CSS class selectors with
`screen.getByText`/`screen.getByRole` queries
- Updated stubs to use semantic `role`/`aria-label` instead of CSS
classes
- Consolidated redundant edge-case tests
- Removed manual `document.body.appendChild` in favor of VTL container
management
- Used distinct mock return values to verify command wiring

### VTU holdouts (2 files)

These files intentionally retain `@vue/test-utils` because their
components use `<script setup>` without `defineExpose`, making internal
computed properties and methods inaccessible via VTL:

1. **`NodeWidgets.test.ts`** — partial VTU for `vm.processedWidgets`
2. **`WidgetSelectDropdown.test.ts`** — full VTU for heavy
`wrapper.vm.*` access

## Follow-up

Deferred items (`ComponentProps` typing, camelCase listener props)
tracked in #10966.

## Review Focus

- Test correctness: all migrated tests preserve original behavioral
coverage
- VTL idioms: proper use of `screen` queries, `userEvent`, and
accessibility-based selectors
- The 2 VTU holdout files are intentional, not oversights

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10965-test-migrate-132-test-files-from-vue-test-utils-to-testing-library-vue-33c6d73d36508199a6a7e513cf5d8296)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: Christian Byrne <cbyrne@comfy.org>

src/composables/useNodeHelpContent.test.ts

@@ -1,10 +1,13 @@
-import { flushPromises } from '@vue/test-utils'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { nextTick, ref } from 'vue'
 
 import { useNodeHelpContent } from '@/composables/useNodeHelpContent'
 import type { ComfyNodeDefImpl } from '@/stores/nodeDefStore'
 
+async function flushPromises() {
+  await new Promise((r) => setTimeout(r, 0))
+}
+
 function createMockNode(
   overrides: Partial<ComfyNodeDefImpl>
 ): ComfyNodeDefImpl {