Create a single-file index.html using Three.js with OrbitCon...

Prompt

Create a single-file index.html using Three.js with OrbitControls & GLTFExporter that procedurally generates unique 3D trees and plants using fractal/L-system branching algorithms on a button click. It should randomize trunk height, thickness, branch angles, leaf density, leaf shape, and seasonal colors (green, autumn hues, flowers). Ensure all mesh geometries are merged properly before export, and include a feature to download the 3D model as .gltf.