Implement, review, or improve SwiftUI animations and transitions. Use when adding implicit or explicit animations with withAnimation, configuring spring animations (.smooth, .snappy, .bouncy), building phase or keyframe animations with PhaseAnimator/KeyframeAnimator, creating hero transitions with matchedGeometryEffect or matchedTransitionSource, adding SF Symbol effects (bounce, pulse, variableColor, breathe, rotate, wiggle), implementing custom Transition or CustomAnimation types, or ensuring animations respect accessibilityReduceMotion.