Adds test coverage for the GPU NMF CLI wiring

[JerryIshihara]

Summary

Adds test coverage for the GPU NMF CLI wiring added to cNMF.

Changes

• Tests GPU CLI argument defaults, validation, and normalization
• Tests that GPU options require --engine gpu
• Tests that GPU engine options are scoped to supported commands
• Tests CPU engine behavior remains unchanged
• Tests GPU engine patching of the cNMF _nmf path
• Tests cNMF factorize passes replicate seeds, component count, run params, and GPU kwargs into the GPU adapter
• Verifies factorize still writes expected spectra outputs