Steps to replicate the issue (include links if applicable):

• skin: vector
• Visit https://test.wikipedia.org/w/index.php?title=User:Novem_Linguae/Scripts/GANReviewTool/GARLog&action=edit
• Click "Preview"

What happens?:

• The portlets along the top of the page (p-views, p-cactions, p-search, p-personal) show on top of the realtime preview panel.

What should have happened instead?:

• Realtime preview panel should be on top of everything

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):

• The fix probably involves CSS z-index