Have non-live articles show a banner when displayed

[LeMurphant]

ref https://discord.com/channels/677546901339504640/1219361047077453845/1235590654512467968

In theory, these articles should not be easily accessible, but if we make a mistake or someone goes to the URL directly, they can reach them, e.g. https://discord.com/channels/677546901339504640/1219361047077453845/1235590654512467968

While I was not able to find the old banner, but I'm quite confident that it used to tell you you were in progress on the old site

IIRC the determining factor to see if it shows on site is Coda, not the Gdocs location