Hybrid: noise/reaction-diffusion-driven Islamic pattern

[GeorgiaSweeny]

Field output selects symmetry group or construction-circle parameters.

Priority-if-short-on-time rank: #3 to cut ("the other two hybrids do not depend on it").

Source: plan-checklist.md, "Aug 6-8: Compositional/hybrid generators" and "Priorities if time runs short".