## Summary
- mark the native mobile List fixture with the production single-pane
class introduced by FN-8754
- add fixture coverage so the production selector cannot drift silently
## Test Plan
- `pnpm --filter @fusion/dashboard exec vitest run
app/__tests__/browser-layout-smoke-fixture.test.ts --silent=passed-only
--reporter=dot`
- `pnpm check:changesets`
- `pnpm build`
- `pnpm --filter @fusion/dashboard test:browser-smoke --
--require-browser`
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Updated the mobile list layout fixture to include the production
single-pane styling class, improving alignment with the app’s mobile
layout behavior.
* **Tests**
* Added a browser smoke test to verify the expected mobile list layout
class is generated reliably.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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