fix: freeze particle gpu state in static mode

src/mbgl/renderer/layers/render_particle_validation_layer.hpp

@@ -7,7 +7,8 @@ namespace mbgl {
 
 class ParticleGpuValidationResources;
 
-// VALIDATION ONLY: proves Core RenderLayer/frame-transform/repaint integration.
+// VALIDATION ONLY: proves Core RenderLayer/GPU ping-pong integration.
+// STATIC redraws only the frozen Trail composite; it never advances State/Trail slots.
 class RenderParticleValidationLayer final : public RenderLayer {
 public:
     explicit RenderParticleValidationLayer(Immutable<style::ParticleValidationLayer::Impl>);