docs: синхронизировать английское руководство (#668)

Английская версия догнана до структуры и содержания русского руководства. Структурный гейт защищает H2-H4 и маркер актуальной версии от нового рассинхрона.

Issue: #668
User-Visible: no

scripts/check-docs.mjs

@@ -6,6 +6,7 @@ import { fileURLToPath } from 'node:url';
 import { DOC_SCREENSHOTS } from '../demo/docs/screenshots.mjs';
 import { visualFingerprint } from './source-fingerprint.mjs';
 import { freshnessSink, screenshotsMode } from './docs-freshness.mjs';
+import { guideParityErrors } from './user-guide-parity.mjs';
 
 const ROOT = resolve(dirname(fileURLToPath(import.meta.url)), '..');
 const EXTERNAL = process.argv.includes('--external');
@@ -184,6 +185,11 @@ for (const [en, ru, required] of [
   }
 }
 
+errors.push(...guideParityErrors(
+  canonicalText(resolve(ROOT, 'docs/USER-GUIDE.md')),
+  canonicalText(resolve(ROOT, 'docs/USER-GUIDE.ru.md')),
+));
+
 const staleTerms = [
   [/\bMarkup (?:tab|mode|editor)\b/gi, 'Plan'],
   [/(?:вкладка|режим|редактор) «Разметка»/gi, '«План»'],

scripts/user-guide-parity.mjs

@@ -0,0 +1,35 @@
+const withoutFences = (text) => text.replace(/^```[^\n]*\n[\s\S]*?^```\s*$/gm, '');
+
+export const guideHeadingProfile = (text) => withoutFences(text)
+  .split(/\r?\n/)
+  .flatMap((line) => {
+    const match = line.match(/^(#{2,4})\s+(.+?)\s*#*\s*$/);
+    if (!match) return [];
+    const section = match[1].length === 2 ? match[2].match(/^(\d+)\./)?.[1] ?? null : null;
+    return [{ level: match[1].length, section }];
+  });
+
+export const guideVersion = (text, language) => {
+  const pattern = language === 'ru'
+    ? /^Актуально для \*\*(v[^*]+)\*\*\./m
+    : /^Current for \*\*(v[^*]+)\*\*\./m;
+  return text.match(pattern)?.[1] ?? null;
+};
+
+export const guideParityErrors = (english, russian) => {
+  const errors = [];
+  const englishProfile = guideHeadingProfile(english);
+  const russianProfile = guideHeadingProfile(russian);
+  if (JSON.stringify(englishProfile) !== JSON.stringify(russianProfile)) {
+    errors.push('docs/USER-GUIDE.md / docs/USER-GUIDE.ru.md: H2-H4 heading profiles differ');
+  }
+
+  const englishVersion = guideVersion(english, 'en');
+  const russianVersion = guideVersion(russian, 'ru');
+  if (!englishVersion || !russianVersion) {
+    errors.push('docs/USER-GUIDE.md / docs/USER-GUIDE.ru.md: current-version marker is missing');
+  } else if (englishVersion !== russianVersion) {
+    errors.push(`docs/USER-GUIDE.md / docs/USER-GUIDE.ru.md: current versions differ (${englishVersion} != ${russianVersion})`);
+  }
+  return errors;
+};