add-scene-warmup

Reduce first-reveal jitter, stutter, frame-time spikes, or FPS drops when meshes enter the camera frustum or become visible in a React Three Fiber WebGPU scene. Use when the user invokes $add-scene-warmup, requests scene precompilation, or reports these first-use symptoms. Supports default Canvas rendering and existing postprocessing passes; not a general fix for sustained low FPS.