perf(web): deduplicate control plane gate state

tools/web/wbv2-failure-ledger.mjs

@@ -0,0 +1,21 @@
+import crypto from "node:crypto";
+import fs from "node:fs";
+import path from "node:path";
+
+const ledgerPath = (root) => path.join(root, "tests/golden/WBV2/failure-ledger.json");
+const keyFor = (entry) => crypto.createHash("sha256").update(JSON.stringify({ task: entry.task, phase: entry.phase, reason: entry.reason, childExit: entry.childExit ?? null })).digest("hex");
+
+export function recordFailure(root, entry) {
+  const file = ledgerPath(root);
+  let ledger = { schemaVersion: 1, entries: [] };
+  try { ledger = JSON.parse(fs.readFileSync(file, "utf8")); }
+  catch { /* First failure or an interrupted write. */ }
+  const key = keyFor(entry);
+  if (ledger.entries.some((candidate) => candidate.key === key)) return false;
+  ledger.entries = [...ledger.entries, { ...entry, key, recordedAt: new Date().toISOString() }].slice(-200);
+  fs.mkdirSync(path.dirname(file), { recursive: true });
+  const temporary = `${file}.tmp-${process.pid}`;
+  fs.writeFileSync(temporary, `${JSON.stringify(ledger, null, 2)}\n`);
+  fs.renameSync(temporary, file);
+  return true;
+}