HOUSE_STYLE was appended after tutor-system.md because the old prompt
never stated which language to teach in, and gpt-oss-20b delivered a
unit-1.1 lesson in Korean. The 16 Sep prompt states the rule outright,
twice — "everything you SAY is in English" — and the client now has
proseIsKorean() to send a Korean explanation back. The appendix said
itself that if the shipped prompt ever covered this, it should go.
{{VARIETY}} also learns the fifth exercise type, recall.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
04a0900a2c