feat(viz): interactive algorithm viz system

frontend/src/components/visualization/step-description.tsx

@@ -0,0 +1,21 @@
+"use client";
+
+import { useVisualization } from "./visualization-context";
+
+export function StepDescription() {
+  const { currentStep } = useVisualization();
+
+  if (!currentStep) {
+    return null;
+  }
+
+  return (
+    <div
+      className="rounded-lg border border-border bg-muted/50 p-4"
+      role="status"
+      aria-live="polite"
+    >
+      <p className="text-sm leading-relaxed">{currentStep.description}</p>
+    </div>
+  );
+}