24 cases: attempt telemetry (start/fail/pass counters, duration), progressive hint sequencing
and exhaustion, hint persistence through a real Lab reset, curriculum stage lock/unlock,
capstone lock-before-prerequisites/unlock-after/random-draw-includes-required-Real-Ops/
cannot-double-start/completion-records-achievement, exam assignment/draw/timer/hint-policy,
cross-student session-read rejection (404, not 403 - consistent with the existing don't-confirm-
existence posture), two-student isolation, timer survives a Lab reset, an assessment session
survives a REAL docker compose restart api, and instructor analytics/needs-attention/RBAC.
Found and fixed two real product bugs in the process: result needed to become nullable (an
in-progress attempt has none yet) and hint_count needed a real DEFAULT 0 (Phase 2B left it
NULL/undefaulted since it wasn't measured yet - it is now, and NULL + 1 stays NULL in SQL).
