fix: verify demo bundle freshness for smokes too

Golden runs, benchmarks and documentation captures each called
assertFreshDemoBundle; the smoke launcher never did, so all ~128 smokes could
silently test a stale demo/srv/assets bundle. On #234 that cost a round of
analysis: three assertions went red and a fourth went green, because the old
code was wrong in two places that agreed with each other, and a mixed result
reads as a logic defect rather than a stale artefact.

launch() now runs the check once for every smoke, against the repository root
rather than the serving root — demo/srv has no src/** to fingerprint.
HP_ALLOW_STALE_BUNDLE=1 skips it for debugging and warns out loud, because a
guard that says nothing when it steps aside is the silent success this project
keeps removing. A mutation entry proves the call cannot quietly disappear.

Issue: #236
User-Visible: no

test/bundle-freshness.test.mjs

@@ -1,9 +1,13 @@
 import assert from 'node:assert/strict';
-import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from 'node:fs';
+import { mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
 import { tmpdir } from 'node:os';
 import { resolve } from 'node:path';
 import test from 'node:test';
-import { assertFreshDemoBundle } from '../demo/bundle-freshness.mjs';
+import {
+  ALLOW_STALE_BUNDLE,
+  assertFreshDemoBundle,
+  assertFreshDemoBundleUnlessAllowed,
+} from '../demo/bundle-freshness.mjs';
 import { sourceFingerprint } from '../scripts/source-fingerprint.mjs';
 
 const fixtureRoot = () => {
@@ -55,3 +59,56 @@ test('bundle freshness uses the target tree fingerprint contract', async () => {
     rmSync(root, { recursive: true, force: true });
   }
 });
+
+test('the launcher gate refuses a stale bundle by default (#236)', async () => {
+  // Смок против несвежего бандла не падает честно: на #234 три проверки
+  // покраснели, а четвёртая ПРОШЛА, потому что старый код одинаково врал в двух
+  // местах, которые сверялись друг с другом. Такой результат читается как
+  // дефект логики и отправляет искать причину не туда.
+  const root = fixtureRoot();
+  try {
+    const stale = { evaluate: async () => 'fingerprint-of-an-older-tree' };
+    await assert.rejects(
+      () => assertFreshDemoBundleUnlessAllowed(stale, root, {}),
+      /stale/,
+    );
+    const fresh = { evaluate: async () => sourceFingerprint(root) };
+    assert.equal(
+      await assertFreshDemoBundleUnlessAllowed(fresh, root, {}),
+      sourceFingerprint(root),
+    );
+  } finally {
+    rmSync(root, { recursive: true, force: true });
+  }
+});
+
+test('the escape hatch skips the gate but never silently (#236)', async () => {
+  const root = fixtureRoot();
+  const warnings = [];
+  const realWarn = console.warn;
+  console.warn = (...args) => warnings.push(args.join(' '));
+  try {
+    const stale = { evaluate: async () => 'stale' };
+    const result = await assertFreshDemoBundleUnlessAllowed(
+      stale, root, { [ALLOW_STALE_BUNDLE]: '1' },
+    );
+    assert.equal(result, null, 'пропуск возвращает null, а не выдуманный фингерпринт');
+    assert.equal(warnings.length, 1, 'пропуск обязан быть слышен');
+    assert.match(warnings[0], new RegExp(ALLOW_STALE_BUNDLE));
+    assert.match(warnings[0], /#236/);
+  } finally {
+    console.warn = realWarn;
+    rmSync(root, { recursive: true, force: true });
+  }
+});
+
+test('the smoke launcher enforces the gate on the repository root (#236)', async () => {
+  // Контракт места вызова: гейт живёт в общем лаунчере, поэтому защита есть у
+  // всех ~128 смоков без правки каждого. И считает фингерпринт по корню
+  // репозитория, а не по каталогу раздачи demo/srv, где нет src/**.
+  const source = readFileSync(
+    new URL('../demo/serve.mjs', import.meta.url), 'utf8',
+  );
+  assert.match(source, /assertFreshDemoBundleUnlessAllowed\(page, REPO_ROOT\)/);
+  assert.match(source, /const REPO_ROOT = dirname\(dirname\(/);
+});