// Tanh-form GELU (pow=3) matching tract's GeluApproximate:
// gelu(x) = 0.5 * x * (1 + tanh(sqrt(2/pi) * (x + 0.044715 * x^3)))
//
// Composed at the kernel level: save the original x, compute the tanh
// argument, call tract's NEON tanh kernel in place, then finish with the
// 0.5 * x * (1 + tanh) multiply. Chunked to keep the scratch buffer L1-resident.
ew_impl_wrap!;