Student eviction UX: warn before lock-break override (MARS-547)

edit-lock-break event 2026-08-22 (e7a4e8dd): student mid-edit on /practicas, JTP broke lock to grade in real time (both on-site, 10min apart), student's unsaved changes lost with no warning. n=2 lifetime (also 2026-07-25), designed tradeoff of MARS-547, not a bug. Product call: should student get any pre-eviction warning/save-draft? Flagged by coder-mars-cc, not currently proposed. Low priority given rarity.