Effective Open Quantum Dynamics with Z₃ Symmetry: Spectral Confinement, Fibonacci Recurrence, and a Falsifiable Prediction

We present an effective field theory framework (TCFU) for open quantum systems with discrete Z₃ symmetry. We show that spectral confinement reduces the dynamics to a 2D invariant subspace, inducing a second-order recurrence structure. Within a defined infrared closure class (TCFU-1/2/3), this recurrence reduces to the Fibonacci form, selecting the golden ratio as a fixed point. A falsifiable prediction is proposed for sub-ohmic environments, distinguishing algebraic from exponential decay.