Practice (random) now picks tasks by ascending difficulty so the first
slot is always level 1 and the session ramps up. Adds ?exclude= to drop
specific subtopics from the random pool, with a per-section checkbox
modal in the UI.
Each task carries a topic_ref (textbook chapter + paragraph) shown as
a 'Учить тему · §N' button next to the solution, deep-linking to the
right section of /textbook/<slug>. Mapping seeded for all 15 math9
subtopics in migration 028.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Maxim Dolgolyov