Kernels cannot declare their own type/const generics

[byeongjee]

kernel.rs:148 rejects every non-lifetime generic parameter on a #[kernel] fn:

#[kernel] fns cannot declare their own type/const generics
(the macro owns `const N: usize` and the exec parameter)

transform_sig then pushes const N: usize and __E onto the parameter list,
and call sites are emitted as ::<N, _> — positional. A user parameter list
would collide with that.