Purge 4 synthetic persona rows - superseded by 'Ver como' view-as

Elazar 2026-07-17: he now has a 'Ver como' (view-as) capability to see what other roles see, so the 4 synthetic persona rows (@pluto-persona.local, switchPersona in src/lib/auth-actions.ts) are no longer needed as his role-switch mechanism. They were HELD as protected under PLUTO-579 precisely because they were the sole view-as path; 'Ver como' supersedes that. Purgeable in a future cleanup pass - NOT now ('for when we get to it'). When actioned: verify Ver como fully covers alumno/jtp/adjunto/titular first, then remove persona rows + switchPersona code + any UI entry point.