ru-RU had only '{{name}} is typing…' but not 'AI agent' / 'AI agent is typing…',
so the Russian typing indicator was mixed-language. Add them (AI-агент / AI-агент
печатает…) grouped with the named key. en-US is already complete; other locales
intentionally keep the en-US fallback (full translation is a separate effort).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>