How-to guides

One task each. No GPU needed unless the task says so.

Guide	Task
Vector/matrix cookbook	Write cross/dot/matmul without reaching for a CUDA math intrinsic anywhere.
Quaternions + runnable notebook	Rotate a vector 90 degrees with a unit quaternion.
Random numbers + runnable notebook	Fill an array with seeded normal draws and prove the stream is reproducible.
Banded emulated double precision	Compute 1/3 with aether::banded::BandedReal and compare it to native double.