I've just had a look at the belt on my car and it doesn't overhang the tensioner pulley like yours does. You can see the pulley is flat with a radius along the edge. The edge of my belt lines up with where the radius ends, ie. it sits on the flat part of the pulley. It look like your tensioner is sitting too close to the engine block by a few mm, and looking at your photo, the edge of the pulley looks very close to the body of the tensioner.
In your photo one can also see a rusty coloured band on the surface of the pulley, I wonder if this is where the belt used to run.
It may be worth taking the belt off and feeling if the tensioner pulley is floating from side to side.