SOP-22 (2nd occurrence): alumno+ayudante dual-role users can't file their own posgrado prácticas — /practicas/nueva treats viewStudents cap (granted by ayudante) as hard isTeacher binary, locking 4 dual-role posgrado students out of self-creation. Fix: decouple teacher/student, explicit creationMode self-vs-forStudent, mode toggle for dual-capable only, single-role unchanged, forStudent stays viewStudents-gated. No DB change. Audit pre-impl review (auth/role path).