Best nut or fruit tree for

Suburban wellington. Tawa to be exact.
I have a sunny corner beside my chicken coop that needs a tree planted in it. It gets sun, reasonable sheltered (as in not too windy). I'm looking for a tree to grow about 2 metres from the boundary, fine to hang over as it is on the top of a 2 metre drop to the neighbours property, at the back of their garden. We are kind of situated in the top part of a sloping gully.

I'm not too sure about drainage, it is damp there in winter underfoot (isn't anywhere?). It won't cast a shadow on anyone's property, there is a huge walnut tree on the other neighbours place about 6 metres away (but unfortunately it doesn't drop nuts on my side).

Am I best to buy a walnut tree (which is really expensive but I do like), or is there another nut tree that will be easy to harvest and enjoy.

Almonds?

I wouldn't recommend planting a walnut tree if the soil is wet in winter. Hazelnuts would do well, as would almonds as long as they are protected from early spring frosts on the blossoms.

Crab apple; mini fruit peach, plum, nectarine trees; smaller kowhai - Dragons Gold?

Thank you. I love almonds and hazelnuts, I'll Google the care of them. Yes, it will get wet feet in winter even though it is on a bank. It is at the bottom of the garden. So walnuts will be out sadly.

feijoas are easy and will have lots of fruit

You may need a pollinator with hazelnuts, I had to buy two. I grew a few blackboy peaches from pits and in the second year I had a few fruits, blackboy does not need another to pollinate and it's a nice tree with great fruit. I made the most wonderful jam and preserves. I have an almond tree which does not need a pollinator and it does not grow tall, I think the name is garden prince.
I have one bb peach in the chicken yard and I will get fruit this year and it will be interesting to watch the chickens with the fruit. I also have an apricot tree in the chicken yard and the chickens left the fruit alone last year.