//! Brush renderer integration and the virtual camera.
//!
//! Pipeline role (PLAN.md, "Pipeline per frame" — render): take the
//! freshly constructed Gaussian list from `splatgen` each frame and hand
//! it to Brush's renderer (WebGPU via Burn), then render it from the
//! virtual camera pose supplied by the UI. Fresh splat list per frame,
//! 30–60 fps target, front-to-back alpha blending.