test(frontend): add dom fixture helpers

docs/frontend-dom-fixtures.md

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+# Frontend DOM Fixture Strategy
+
+This guide outlines how to reproduce the markup emitted by the Django templates while running Vitest in jsdom.  The aim is to make it straightforward to write integration-style unit tests for managers and UI helpers without having to duplicate template fragments inline.
+
+## Loading Template Markup
+
+Vitest executes inside Node, so we can read the same HTML templates that ship with the extension:
+
+1. Use the helper utilities from `tests/frontend/utils/domFixtures.js` to read files under the `templates/` directory.
+2. Mount the returned markup into `document.body` (or any custom container) before importing the module under test so its query selectors resolve correctly.
+
+```js
+import { renderTemplate } from '../utils/domFixtures.js'; // adjust the relative path to your spec
+
+beforeEach(() => {
+  renderTemplate('loras.html', {
+    dataset: { page: 'loras' }
+  });
+});
+```
+
+The helper ensures the dataset is applied to the container, which mirrors how Django sets `data-page` in production.
+
+## Working with Partial Components
+
+Many features are implemented as template partials located under `templates/components/`.  When a test only needs a fragment (for example, the progress panel or context menu markup), load the component file directly:
+
+```js
+const container = renderTemplate('components/progress_panel.html');
+
+const progressPanel = container.querySelector('#progress-panel');
+```
+
+This pattern avoids hand-written fixture strings and keeps the tests aligned with the actual markup.
+
+## Resetting Between Tests
+
+The shared Vitest setup clears `document.body` and storage APIs before each test.  If a suite adds additional DOM nodes outside of the body or needs to reset custom attributes mid-test, use `resetDom()` exported from `domFixtures.js`.
+
+```js
+import { resetDom } from '../utils/domFixtures.js';
+
+afterEach(() => {
+  resetDom();
+});
+```
+
+## Future Enhancements
+
+- Provide typed helpers for injecting mock script tags (e.g., replicating ComfyUI globals).
+- Compose higher-level fixtures that mimic specific pages (loras, checkpoints, recipes) once those managers receive dedicated suites.