URL-param / env-var / default precedence ladder for backend
selection. The result drives whether createWebGLRenderer or
createWebGPURenderer is invoked. Kept as a pure function so
the selection logic is unit-testable independent of WebGL /
WebGPU construction.
URL-param / env-var / default precedence ladder for backend selection. The result drives whether
createWebGLRendererorcreateWebGPURendereris invoked. Kept as a pure function so the selection logic is unit-testable independent of WebGL / WebGPU construction.