MCQ drill

Part of oahelper-mcp by Sirjan Singh.

1. Load questions

1. oahelper_offline(company). If there are no MCQ sets saved, oahelper_sync(company).
2. MCQ answer keys live in the question files under library/<co>/questions/, in the ## MCQ answers section. Read those files; do not refetch.
3. If the user named a topic (OS, DBMS, networks, aptitude, output prediction, SQL), filter to it. Otherwise draw from the newest sets first.
4. Skip questions marked correct in library/_progress.md unless the user asks for a full pass.

2. Drill loop