feat(viz): heap pattern with kth largest

frontend/src/components/visualizations-new/primitives/heap-node.tsx

@@ -0,0 +1,87 @@
+'use client';
+
+import { motion } from 'framer-motion';
+import { cn } from '@/lib/utils';
+import type { HeapNodeState } from '@/lib/visualizations/types';
+
+interface HeapNodeProps {
+  node: HeapNodeState;
+  x: number;
+  y: number;
+  radius?: number;
+  className?: string;
+}
+
+const STATE_CLASSES = {
+  normal: 'fill-[var(--surface-variant)] stroke-[var(--border)]',
+  comparing: 'fill-[var(--info)]/20 stroke-[var(--info)]',
+  swapping: 'fill-[var(--warning)]/20 stroke-[var(--warning)]',
+  settled: 'fill-[var(--success)]/20 stroke-[var(--success)]',
+  highlighted: 'fill-[var(--primary)]/30 stroke-[var(--primary)]',
+  removing: 'fill-[var(--destructive)]/20 stroke-[var(--destructive)] opacity-50',
+} as const;
+
+const TEXT_CLASSES = {
+  normal: 'fill-[var(--foreground)]',
+  comparing: 'fill-[var(--info)]',
+  swapping: 'fill-[var(--warning)]',
+  settled: 'fill-[var(--success)]',
+  highlighted: 'fill-[var(--primary)]',
+  removing: 'fill-[var(--destructive)] opacity-50',
+} as const;
+
+export function HeapNode({
+  node,
+  x,
+  y,
+  radius = 24,
+  className,
+}: HeapNodeProps) {
+  const isActive = node.state === 'comparing' || node.state === 'swapping' || node.state === 'highlighted';
+  const isRemoving = node.state === 'removing';
+
+  return (
+    <motion.g
+      initial={false}
+      animate={{
+        scale: isActive ? 1.1 : isRemoving ? 0.8 : 1,
+        opacity: isRemoving ? 0.5 : 1,
+      }}
+      transition={{
+        type: 'spring',
+        stiffness: 300,
+        damping: 30,
+      }}
+      style={{ transformOrigin: `${x}px ${y}px` }}
+      className={cn(className)}
+    >
+      <motion.circle
+        cx={x}
+        cy={y}
+        r={radius}
+        strokeWidth={2}
+        className={cn(
+          'transition-colors duration-200',
+          STATE_CLASSES[node.state]
+        )}
+        initial={false}
+        animate={{
+          filter: isActive ? 'drop-shadow(0 0 8px var(--primary))' : 'none',
+        }}
+        transition={{ duration: 0.2 }}
+      />
+      <text
+        x={x}
+        y={y}
+        textAnchor="middle"
+        dominantBaseline="central"
+        className={cn(
+          'pointer-events-none select-none font-mono text-sm font-medium',
+          TEXT_CLASSES[node.state]
+        )}
+      >
+        {node.value}
+      </text>
+    </motion.g>
+  );
+}