feat: add agent API and operational analytics

src/database/client.ts

@@ -201,6 +201,22 @@ export function runMigrations(db: Database.Database): void {
       `);
     },
     () => migrateAccountOwnership(db),
+    () => {
+      addColumnIfNotExists(db, 'sent_messages', 'experiment_id', 'TEXT');
+      addColumnIfNotExists(db, 'sent_messages', 'prompt_version', 'TEXT');
+      addColumnIfNotExists(db, 'sent_messages', 'model_id', 'TEXT');
+      addColumnIfNotExists(db, 'sent_messages', 'selection_reason', 'TEXT');
+      addColumnIfNotExists(db, 'sent_messages', 'source_type', 'TEXT');
+      db.exec(`
+        CREATE INDEX IF NOT EXISTS idx_sent_messages_experiment
+          ON sent_messages(account_id, experiment_id, strategy_id, sent_at);
+        CREATE TABLE IF NOT EXISTS recipient_suppressions (
+          recipient TEXT PRIMARY KEY COLLATE NOCASE,
+          reason TEXT NOT NULL,
+          created_at INTEGER NOT NULL
+        );
+      `);
+    },
   ];
 
   let currentVersion = db.pragma('user_version', { simple: true }) as number;