These chairs are from Bermex. They're not the same as the chairs that you posted, but they are very good quality. FYI, you can change the style of the leg as well as the wood finish and fabric. You can also send them your own fabric to use, although the company is in Canada so it might get tricky with customs, etc. Here is a link that might be useful: Bermex chair

I perused my Ideabooks and the chair rail butts up to a narrow glass stationary panel, a metal frame, or a short wall built on two sides of the shower. I assume the last rail piece has a bullnosed end. Then you use the same piece to start the run of rail inside the shower. This is interesting where they made a right angle with the chair rail tile, which would allow you to not continue it into the shower.

https://www.zillow.com/homes/for_sale/20748946_zpid/2000000-2500000_price/8269-10337_mp/globalrelevanceex_sort/34.134328,-118.203364,34.051308,-118.330393_rect/12_zm/0_mmm/

"What could cause this to happen?" It's more an issue with the hinge screws not being anchored to the wall framing versus the marble not being properly installed. With the weight and moment of the door pulling on the upper hinge, and with the hinges only being secured to the "marble slab", it caused the slab to separate from the wall. " How can it be fixed?" As has been discussed,if you can add blocking from behind, do it. Reset the slab so it's tight to the backer, then run longer hinge screws through the slab and into the framing. " Who should fix it?" Your GC from the original build is responsible for the details, or in this case, the lack thereof. He should have seen this coming. Ultimately, the GC is responsible for the failure. The guy who installed the marble, it's really not his worry. The glass installer, he should have known that screws set only in a wall slab would not be sufficient long term. The failure is on the GC and the glass guy, partially on the glass guy for not raising an objection. The repair? You'll want to hire someone new to install the blocking and repair the drywall. If your GC is still around, ring him up. Then have the glass guy back to properly anchor the hinges in to the new blocking.