I think a little liner piece of tile would be an idea, though I am not a tile expert.

The space should be filled with cut tile, and you would use caulk, not grout at the very top. Does the gap vary in thickness around the room?

Caulk it and forget it.

With that tile, I would have cut the last 4 rows or so from the mesh and made the grout lines a poo wider to make it disappear. Much more imperceptible than a cut tile which is not a good idea.

Or.....paint it the same as the ceiling and it will appear as if it is part of the ceiling.

I agree with kelleg for my second choice. A very thin liner.

Side story: Things happen. We redid our backsplash because my first choice looked horrible. The installation was perfect. So, when our same contractor came back to do it a second time, I expected it to look the same. Different subway tile, but same plan. I wound up with slivers in the corners! I was told that in this installation it was un avoidable. Mmmmm. Anyway, I put my Keurig in the corner and it is now a non issue.

Let us know what you decide. Beautiful tile! And, the fact that you did it yourself is amazing.

Question Joseph. Should Tiber have started from the top and go down? That way if there is an issue it would be hidden behind the molding?

Generally you want whole tiles at the counter level where they are seen, but moulding raises the issue, will there be crown moulding? If so, problem solved.

If you feel that you need something to cover the caulk, maybe a narrow piece of stainless steel trim to match the hood chimney?

Caulk it and when you touch up the ceiling, bring the paint down, just a little bit, very impossibly neatly. It really looks pretty nice already.

I also have this problem.. Stone guys cut the slab between .25 and .50 inches short.. Cant get replacement stone, so we calked and brought the ceiling paint down over the grout. i dont like it and others have noticed. My next fix is to use this self sticking pvc stainless steel color (many other color finishes available) trim to mitigate the gap. Her is the Home Depot link, but I also found the exact same product on Amazon for the same price. pack of 3 - 24” pieces for $19.99:

https://www.homedepot.com/p/Aspect-Stainless-24-in-Vinyl-Backsplash-Trim-3-Pack-935-50/313854875#overlay