Shallow moments

Shallow moments in 1-D recover the vertical structure of a 2-D flow; in 2-D they are essentially our 3-D model. The dimensionality is set by the mesh.

	What it covers
Moments in 2-D	Write your own closure, inject it into SME, run in 2-D, and read the vertical velocity profile back out.

Runs on the reference NumPy backend — pip install zoomy_core, no container.