fix(examples): replace hand-written examples with real benchmark output

The examples/ before/after blocks were authored by hand, not produced by a
model. Issue #127 correctly noted that nobody hand-rolls quicksort for "sort
this array" - every model just calls .sort(). Regenerate all examples verbatim
from a real benchmark run (Claude Haiku 4.5, no-skill arm vs ponytail arm,
benchmarks/output.json) so the before/after is reproducible, not authored:

  email 75->3, debounce 116->10, csv 20->3, countdown 267->9, rate-limit 128->10 LOC

- Delete sorting.md (pure strawman) plus the other hand-written caricatures
  (api-endpoint, caching, date-picker)
- Add benchmarks/generate-examples.mjs to regenerate examples from any run
- examples/README.md indexes the set and documents how to reproduce

Closes #127

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

benchmarks/generate-examples.mjs

@@ -0,0 +1,63 @@
+// Generate examples/*.md verbatim from a real benchmark run (output.json):
+// each file shows the same task answered with no skill vs with ponytail, same model.
+//   node benchmarks/generate-examples.mjs
+import { readFileSync, writeFileSync } from 'node:fs';
+import loc from './loc.js';
+
+const j = JSON.parse(readFileSync(new URL('./output.json', import.meta.url), 'utf8'));
+const isHaiku = (id) => id.includes('haiku');
+
+const meta = [
+  [/validates email/, 'email-validation', 'Email Validation'],
+  [/debounce/,        'debounce',         'Debounce'],
+  [/sales\.csv/,      'csv-sum',          'CSV Sum'],
+  [/countdown timer/, 'react-countdown',  'Countdown Timer'],
+  [/rate limiting/,   'rate-limit',       'Rate Limiting'],
+];
+
+const pick = (re, armIdx) =>
+  j.results.results.find((r) => isHaiku(r.provider.id) && r.promptIdx === armIdx && re.test(r.vars.task));
+
+const rows = [];
+for (const [re, slug, title] of meta) {
+  const b = pick(re, 0), p = pick(re, 2);
+  if (!b || !p) { console.log('MISS', slug, !!b, !!p); continue; }
+  const bL = loc(b.response.output).score, pL = loc(p.response.output).score;
+  const md = `# ${title}
+
+**Task:** "${b.vars.task}"
+
+Verbatim model output from a benchmark run — Claude Haiku 4.5, no-skill arm vs ponytail arm, temperature 1, source \`benchmarks/output.json\`. Reproduce: \`npx promptfoo@latest eval -c benchmarks/promptfooconfig.yaml\`.
+
+## Without Ponytail — ${bL} lines of code
+
+${b.response.output.trim()}
+
+## With Ponytail — ${pL} lines of code
+
+${p.response.output.trim()}
+
+**${bL} → ${pL} lines of code** — same model, same prompt.
+`;
+  writeFileSync(new URL(`../examples/${slug}.md`, import.meta.url), md);
+  rows.push([title, slug, bL, pL]);
+  console.log('wrote examples/' + slug + '.md', bL, '->', pL);
+}
+
+const tbl = rows.map(([t, s, b, p]) => `| [${t}](${s}.md) | ${b} | ${p} |`).join('\n');
+const readme = `# Examples
+
+Real model output, verbatim from benchmark runs — the same task answered by the same model
+with no skill (\`## Without Ponytail\`) and with ponytail (\`## With Ponytail\`), so you can
+compare side by side. Model: Claude Haiku 4.5, temperature 1, source \`benchmarks/output.json\`.
+
+These are not hand-written. Reproduce them yourself:
+\`npx promptfoo@latest eval -c benchmarks/promptfooconfig.yaml\`. Method, all three models, and
+median-of-10 numbers: [../benchmarks/](../benchmarks/).
+
+| Example | Without (LOC) | With (LOC) |
+|---|--:|--:|
+${tbl}
+`;
+writeFileSync(new URL('../examples/README.md', import.meta.url), readme);
+console.log('wrote examples/README.md');