[meta.reflection.result] move declaration of TCls earlier

[jwakely]

Fixes NB US 117-178 (C++26 CD).

Fixes https://github.com/cplusplus/nbballot/issues/747

But I wonder if we should name this something other than TCls seeing as that name is used for a class template in at least five examples elsewhere in reflection wording. Maybe the invented template here should have a different name to avoid any risk of confusion.

[eisenwave]

What is the rationale for the name TCIs anyway?

Maybe something like CTP (constant template parameter) would work? After all, it seems like CTP is really just being used to wrap a constant template parameter here. If you wanted to, you could also use std::nontype/std::constant_arg and wouldn't need to invent any class template.

Anyhow, the current change looks correct and like a clear improvement.

[jwakely]

It's TCls with an L not TCIs with i

It's short for "template class", but any other name except T would work here.