## Summary
- Add `ModelLibraryHelper` mock helper for `/experiment/models` and
`/view_metadata` endpoints
- Add `ModelLibrarySidebarTab` page object fixture with search, folder,
and leaf locators
- Add 11 E2E test scenarios covering tab open/close, folder display,
folder expansion, search with debounce, refresh, load all folders, and
empty state
## Test plan
- [ ] CI passes all Playwright shards
- [ ] `pnpm typecheck:browser` passes
- [ ] `pnpm lint` passes
┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10789-test-modelLibrary-add-E2E-tests-for-model-library-sidebar-tab-3356d73d365081b49a7ed752512164da)
by [Unito](https://www.unito.io)
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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
