Comment notification quotes empty-content comments and fires on aprobado practicas

SOP-PLUTO-12 root cause. A JTP (Silvia Toranzo) received "Nuevo comentario del alumno - HC 86579" quoting a comment whose literal text was "Sin comentarios", on a practica already in reviewState=aprobado, and read it as an announcement about changing her asistente. Two defects: (1) the mail quotes a null-content comment as if it were content - no guard for placeholder/empty-ish bodies; (2) comment notifications keep paging the assigned JTP after the practica is aprobado, which is a product question about whether a closed practica should still notify. Evidence: db-pluto-cc prod reads 2026-08-17 - vPracticaComentarios shows two comments at 19:01:50 and 19:01:53 UTC on 2026-08-07, outbox row sent 19:01:58, ticket filed 22:02. Practica 3c922125-a9cd-419a-91fc-b0090cf0e389, HC 86579.