[ci] run stylelint as part of CI tests (#6143)

## Summary

Final PR continuing from

- https://github.com/Comfy-Org/ComfyUI_frontend/pull/5926
- https://github.com/Comfy-Org/ComfyUI_frontend/pull/5940

actually run stylelint in lint workflows.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6143-ci-run-stylelint-as-part-of-CI-and-pre-commit-hook-2916d73d3650811891bcc9f94379cc5f)
by [Unito](https://www.unito.io)

---------

Co-authored-by: DrJKL <DrJKL@users.noreply.github.com>

.github/workflows/ci-lint-format.yaml

@@ -39,6 +39,9 @@ jobs:
       - name: Run ESLint with auto-fix
         run: pnpm lint:fix
 
+      - name: Run Stylelint with auto-fix
+        run: pnpm stylelint:fix
+
       - name: Run Prettier with auto-format
         run: pnpm format
 
@@ -63,6 +66,7 @@ jobs:
       - name: Final validation
         run: |
           pnpm lint
+          pnpm stylelint
           pnpm format:check
           pnpm knip