chore: import upstream snapshot with attribution

scripts/check/check-duplication.mjs

@@ -0,0 +1,75 @@
+#!/usr/bin/env node
+// scripts/check/check-duplication.mjs
+// Catraca de duplicação de código. Roda jscpd@4 (PINADO — o v5 é um rewrite Rust com
+// CLI/JSON incompatíveis) sobre src+open-sse e compara a % atual contra um baseline
+// congelado (duplication-baseline.json). Falha se a duplicação SUBIR. Ataca a assinatura
+// nº1 de slop de IA (GitClear 2026: duplicação 4-8x na era IA) — no nosso caso, o
+// copy-paste dos executors (48/50 sobrescrevem execute() inteiro). --update ratcheta.
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { execFileSync } from "node:child_process";
+import { pathToFileURL } from "node:url";
+
+const ROOT = process.cwd();
+const BASELINE_PATH = path.resolve(
+  process.argv.includes("--baseline")
+    ? process.argv[process.argv.indexOf("--baseline") + 1]
+    : path.join(ROOT, "config/quality/duplication-baseline.json")
+);
+const UPDATE = process.argv.includes("--update");
+const EPS = 0.05; // tolerância de ruído de float (jscpd é determinístico; isto é margem)
+// Use local binary (pinned in package.json devDependencies — no registry download at CI time)
+const JSCPD_BIN = path.join(ROOT, "node_modules", ".bin", "jscpd");
+const JSCPD_FIXED_ARGS = [
+  "src",
+  "open-sse",
+  "--reporters",
+  "json",
+  "--silent",
+  "--min-tokens",
+  "50",
+  "--ignore",
+  "**/*.test.ts,**/*.test.tsx,**/__tests__/**",
+];
+
+/** Avalia a % atual contra o baseline. */
+export function evaluateDuplication(current, baseline, eps = EPS) {
+  return {
+    regressed: current > baseline + eps,
+    improved: current < baseline - eps,
+  };
+}
+
+function measureDuplicationPct() {
+  const out = fs.mkdtempSync(path.join(os.tmpdir(), "jscpd-"));
+  execFileSync(JSCPD_BIN, [...JSCPD_FIXED_ARGS, "--output", out], { stdio: "ignore" });
+  const report = JSON.parse(fs.readFileSync(path.join(out, "jscpd-report.json"), "utf8"));
+  return report.statistics.total.percentage;
+}
+
+function main() {
+  if (!fs.existsSync(BASELINE_PATH)) {
+    console.error(`[duplication] FAIL — ${path.basename(BASELINE_PATH)} ausente.`);
+    process.exit(2);
+  }
+  const baseline = JSON.parse(fs.readFileSync(BASELINE_PATH, "utf8"));
+  const current = measureDuplicationPct();
+  const { regressed, improved } = evaluateDuplication(current, baseline.percentage, EPS);
+
+  if (UPDATE && improved) {
+    baseline.percentage = current;
+    fs.writeFileSync(BASELINE_PATH, JSON.stringify(baseline, null, 2) + "\n");
+    console.log(`[duplication] baseline ratcheado: ${current}% (era ${baseline.percentage}%)`);
+  }
+  if (regressed) {
+    console.error(
+      `[duplication] REGRESSÃO — ${current}% > baseline ${baseline.percentage}% (+${EPS} tolerância)\n` +
+        `  → extraia o trecho duplicado (helper compartilhado) ou ajuste duplication-baseline.json com justificativa.`
+    );
+    process.exit(1);
+  }
+  console.log(`[duplication] OK — ${current}% (baseline ${baseline.percentage}%)`);
+}
+
+if (import.meta.url === pathToFileURL(process.argv[1] || "").href) main();