docs(extending-modx): audit security, services and snippets against 3.x code, editorial pass, en/ru sync

[Ibochkarev]

What

Fact-check, editorial pass and locale sync of extending-modx/{security,services,snippets} — 12 pages (en + ru) against the 3.x code.

Fact sync (reports in .temp/docs-review/sync-2026-10-14-{security,services,services,snippets}.md)

• 22/22 STALE, 2/2 PHANTOM, 1/1 ORPHAN, 18/18 UNDOCUMENTED groups resolved.
• http: both return examples fixed to return print_r($body, true);; modrest: deprecated notice added, headings renamed to match the actual code.
• modregistry: MODX 2.1 note dropped, default branch fixed, message_limit default 20 → 200 (matches Read.php), send/read parameter lists re-checked.
• UNVERIFIABLE items removed (hundreds/eLance, WordPress comparison); the speed claim in good-chunk and the modRest deprecation note remain pending a decision.

Editorial pass

• EN 9 592 → 7 283 words (−24%): cut water, duplicated "See also" self-links, WP analogies, scenario filler; reference and "Вывод" blocks trimmed.
• All FACT?/EXAMPLE? markers resolved; reference examples aligned with the current code.

Locales

• ru fully synced with en: headings, code fences, link sets and paragraph parity verified 12/12; translated tables for modregistry, warnings as ::: warning containers.

Verification

• Internal links checked in both locales, 0 broken; 47 MEDIA markers stripped (job in .temp/docs-review/media-todo.md).
• No code bugs found — no upstream issues filed.