Use when translating or localizing UI strings, marketing copy, documentation, or any source text into Vietnamese (Tiếng Việt). Isolating — NO gender, number, case, or conjugation. Enforces the six-tone diacritic system (never strip tone marks), the classifier system before counted nouns (một cái bàn, một con mèo), pronoun-based formality with bạn as UI default, adjective-after-noun order (tệp mới), softening particles (never in buttons), progressive `đang` for status (Đang tải…), active over `được` passive, DD/MM/YYYY, VND (100.000₫), and no colloquial shortenings.
