Revert "merge: integrate extension auto-update"

This reverts commit 322475860a, reversing
changes made to f52d9d7413.

control-plane/src/db.ts

@@ -5,7 +5,7 @@ import { writeEmergencyDiagnostic } from './diagnostics.js';
 const { Pool } = pg;
 let pool: pg.Pool | null = null;
 
-export const REQUIRED_SCHEMA_VERSION = '019_extension_host_updates';
+export const REQUIRED_SCHEMA_VERSION = '018_agentbus_account_workers';
 
 export interface DatabaseReadiness {
   ready: boolean;