plain_persian() strips kasra/fatha/damma/shadda/sukun/hamza-above and the written «هی» ezafe, keeping tanwin. Applied
at output, not in data: PlainPersianJSONRenderer runs one byte-level pass over every JSON response (~5 ms per MB
locally), and to_plain() cleans tutor answers including the stream. Rewriting titles in the DB/seed would have broken
question binding by title path and SeedRecord keys. Tests updated to expect the cleaned text; config/tests_plain_persian.py.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
