Interactive WebGPU soft-body octopus study with jelly layers

GOAL: Make an interactive WebGPU soft-body study of an octopus cast in two layers of jelly, in the same studio style as the tiger shark jelly: a domed head with eyes in raised sockets (golden iris, horizontal bar pupil) and a small horn over each, a big soft mantle leaning back, a funnel on the flank, and a web joining eight arms. Each arm is a chain of tapering capsules laid out by integrating curvature: a gentle sweep across the table, then the outer third rolls up off the table into a curl so the two staggered rows of pale suckers face out. The underside of every arm is a milky layer, the back has a chromatophore mottle and small papillae. XPBD tetrahedral sim with firmer arm tips; muscle strain makes the arms writhe (sideways bending waves out along each arm, phased arm to arm) and curl up and let go. Drag to stretch and lift, drop bait beads, three colourways (coral, plum, mint), live mass, volume, arm span and mantle height readouts.