I have not seen a chair that could fold into a coffee table. But it would be possible to have a folding chair that could fit under a coffee table or just lean up somewhere.
I have a similar search. I will soon be getting an open plan (not a separate garage) toy hauler where half of it is just a big empty box when unloaded. Unfortunately, the furniture options in these toy haulers are often designed to sleep way too many people and do a poor job during the day as furniture. I have been searching for folding furniture, but most of what I see is folding furniture intended for outdoor use. It would be entirely different design and materials if the folding furniture was designed for indoor use only, but obviously there is not a big market for that.
I have found an interesting company, Stakmore (Meco), that manufactures in Greeneville TN. Here are their folding chairs, they also have folding tables.
http://www.stakmore.com/products.aspx?cat=Folding%20ChairsIf anyone knows of other indoor folding furniture producers, please post a link.
thanks,
Fred