Faithful TypeScript port of the a-immersive visualiser
(deployments/meml-aimmersive/js/ui/visualizer.js): 400 particles, identical
value-noise + 20-output param mapping + advection/attractor/dispersion/repulsor
integration. ParticleStage renders the full-bleed canvas (driven by engine
outputs each rAF) plus the macro-axis bar and a corner input pad.
