N-independence diagnostic: representation-sensitivity scoring rule

[jc-macdonald]

Julia port of the N-independence diagnostic from the representation-matters framework.

Motivation

Same as model-criticism (Python) #38: the representation-matters paper formalises the category error "is N part of the biology, or part of the numerics?" — the N-independence test is a model criticism tool.

Tasks

• Define RepresentationSensitivity <: ScoringRule type
• Implement N-sweep runner using Julia's parametric dispatch
• Compute stability metric across N values for a given observable
• Integration test with a simple mixture ODE (OrdinaryDiffEq.jl)

Cross-references

• model-criticism #38 (Python equivalent)
• representation-matters run_adaptive(): multi-objective search via Metaheuristics.jl #12 (Theorem 4: N-independence diagnostic)