feat: add ponytail skill, examples, README

examples/sorting.md

@@ -0,0 +1,42 @@
+# Sorting
+
+**Task:** "Sort this array of numbers."
+
+## Without Ponytail
+
+```js
+function quickSort(arr, compareFn = (a, b) => a - b) {
+  if (arr.length <= 1) return arr;
+
+  const pivot = arr[Math.floor(arr.length / 2)];
+  const left = [];
+  const right = [];
+  const equal = [];
+
+  for (const item of arr) {
+    const cmp = compareFn(item, pivot);
+    if (cmp < 0) left.push(item);
+    else if (cmp > 0) right.push(item);
+    else equal.push(item);
+  }
+
+  return [
+    ...quickSort(left, compareFn),
+    ...equal,
+    ...quickSort(right, compareFn),
+  ];
+}
+
+const sorted = quickSort(numbers);
+```
+
+A hand-rolled quicksort. It allocates three arrays per recursion level, blows the stack on large inputs, and replaces an engine-optimized native sort with homework.
+
+## With Ponytail
+
+```js
+// ponytail: this exists
+numbers.sort((a, b) => a - b)
+```
+
+**24 lines → 1 line.** Every runtime ships a sort tuned by people whose whole job is sorting. Use it.