Enhance queue processing and recovery mechanisms

- Implement auto-recovery of orphaned queues on startup in WorkerService.
- Introduce startSessionWithAutoRestart method for continuous processing of pending work.
- Modify SDKAgent to prevent session deletion during processing to avoid race conditions.
- Update SessionManager to allow continued processing after yielding summaries.
- Add logic in SessionRoutes to mark processing messages as failed upon generator errors.
- Create detailed documentation for the queue system logic, including recovery mechanisms and potential issues.

src/services/worker/SDKAgent.ts

@@ -164,8 +164,8 @@ export class SDKAgent {
       }
       throw error;
     } finally {
-      // Cleanup
-      this.sessionManager.deleteSession(session.sessionDbId).catch(() => {});
+      // NOTE: Do NOT delete session here - SessionRoutes.finally() handles cleanup
+      // and auto-restart logic. Deleting here races with pending work checks.
     }
   }