Generated-question funnel for corpora with no assessment material

[pequalsnp]

Most corpora carry no assessment material, so bank-first extraction alone would make etude a tool for one lucky kind of course.

Generate questions for those corpora — through a funnel, never live during a drill:

1. draft candidate questions from a lesson (the existing rag enrichment path)
2. iterate: critique-revise and a scored tournament, converging rather than accepting a first draft
3. staged human review — accept / edit / reject, the family's proven gate
4. admit survivors to the bank, permanently labelled generated

Hard rules:

• the drill never invents a question at ask time, whatever the source
• extracted and generated items are never silently mixed; provenance shows in the UI and in reports
• a generated item's "official answer" is a reviewed answer, and the wording should not pretend otherwise

Depends on qbank (#4) for the bank format and stable IDs.