Renders a radial-gradient vignette (darkened edges) whose intensity pulses between subtle and strong using Math.sin() on useCurrentFrame(). Layer over any scene to add mood, focus attention toward the centre, or create tension.
Pulse speed, min/max intensity, and vignette shape are configurable. The component is a pure overlay — it positions itself absolutely over child content with pointer-events: none, so it composes cleanly with any scene.