Add coupled Floquet demo variants

Author: famiuer

content/blog/nonlinear-system-study/index.md

@@ -20,5 +20,8 @@ If you want to play with them directly:
 - [Torus oscillator and Poincare section](/nonlinear/torus_oscillator.html)
 - [Floquet stability and parametric resonance](/nonlinear/floquet.html)
 - [Floquet phase portrait variant](/nonlinear/floquet2.html)
+- [Coupled Floquet v0](/nonlinear/coupled_floquet.html)
+- [Coupled Floquet v1](/nonlinear/coupled_floquet2.html)
+- [Coupled Floquet v2](/nonlinear/coupled_floquet3.html)
 
 Nothing fancy, just practical visual notes I can revisit later. I’ll keep adding more as I go.