test: prepare phase 9 requalification harness and blocker register

docs/redesign/phase-9/p9-requal-01/performance/metrics.mjs

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+import assert from 'node:assert/strict';
+import { performance } from 'node:perf_hooks';
+import { setTimeout as sleep } from 'node:timers/promises';
+
+export const durationMs = 15 * 60 * 1000;
+export const paceMs = 500;
+
+export function summarize(rows) {
+  const values = rows.filter(row => !row.error && row.status === 200).map(row => row.ms).sort((a, b) => a - b);
+  const percentile = p => values.length ? values[Math.ceil(values.length * p) - 1] : null;
+  return { attempts: rows.length, failures: rows.filter(row => row.error || row.status !== 200).length,
+    p50Ms: percentile(.5), p95Ms: percentile(.95), p99Ms: percentile(.99), maxMs: values.at(-1) ?? null };
+}
+
+export async function waitUntil(target) {
+  while (performance.now() < target) await sleep(Math.min(1000, target - performance.now()));
+}
+
+export function assertMembership(actual, expected) {
+  assert.equal(actual.length, 250);
+  assert.equal(new Set(actual).size, 250);
+  assert.deepEqual([...actual].sort((a, b) => a - b), [...expected].sort((a, b) => a - b));
+}
+
+if (process.argv.includes('--self-test')) {
+  assert.equal(durationMs, 900000);
+  assert.equal(paceMs, 500);
+  assert.deepEqual(summarize([]), { attempts: 0, failures: 0, p50Ms: null, p95Ms: null, p99Ms: null, maxMs: null });
+  const rows = Array.from({ length: 100 }, (_, i) => ({ ms: i + 1, status: 200 }));
+  assert.deepEqual(summarize([...rows, { ms: 999, status: 500 }, { ms: 999, error: 'timeout' }]),
+    { attempts: 102, failures: 2, p50Ms: 50, p95Ms: 95, p99Ms: 99, maxMs: 100 });
+  const ids = Array.from({ length: 250 }, (_, i) => i + 1);
+  assertMembership(ids.toReversed(), ids);
+  assert.throws(() => assertMembership([...ids.slice(0, 249), 1], ids));
+  assert.throws(() => assertMembership([...ids.slice(0, 249), 999], ids));
+  assert.throws(() => assertMembership(ids.slice(1), ids));
+  console.log('performance metrics self-check passed');
+}