Remove sender_type and receiver_type from log.messages

schemas/04_log.sql

@@ -10,7 +10,6 @@ CREATE SCHEMA log;
 CREATE EXTENSION IF NOT EXISTS pgcrypto;
 
 -- Tipos
-CREATE TYPE log.actor_type AS ENUM ('user', 'agent', 'orchestrator', 'system', 'tool');
 CREATE TYPE log.ref_type AS ENUM ('context', 'accountant', 'secretary');
 
 -- ============================================
@@ -21,9 +20,7 @@ CREATE TABLE log.messages (
     hash            CHAR(64) UNIQUE NOT NULL,
     session_hash    CHAR(64) NOT NULL,
     thread_hash     CHAR(64),
-    sender_type     log.actor_type NOT NULL,
     sender_id       CHAR(64) NOT NULL,
-    receiver_type   log.actor_type NOT NULL,
     receiver_id     CHAR(64) NOT NULL,
     leader_id       CHAR(64),
     role            TEXT,