- _query_teacher_classes: fix code -> class_code (Supabase column name), add section_id param
- _build_timetable_section: tag class nodes with section_id=timetable
- _build_classes_section: tag class nodes with section_id=classes
- SubjectClass handler: section=timetable -> taught_lessons for class; section=classes -> enrolled students
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>