Add orchestrator types and error handling configurations

- Introduced new TypeScript types for orchestrator functionality, including `SessionStrategy`, `ErrorHandlingStrategy`, and `OrchestrationStep`.
- Defined interfaces for `OrchestrationPlan` and `ManualOrchestrationParams` to facilitate orchestration management.
- Added a new PNG image file for visual representation.
- Created a placeholder file named 'nul' for future use.

ccw/frontend/src/components/issue/queue/QueueItemExecutor.tsx

@@ -210,7 +210,7 @@ export function QueueItemExecutor({ item, className }: QueueItemExecutorProps) {
       const flowForStore: Flow = {
         ...flowDto,
         version: Number.isFinite(parsedVersion) ? parsedVersion : 1,
-      } as Flow;
+      } as unknown as Flow;
       useFlowStore.getState().setCurrentFlow(flowForStore);
 
       // Execute the flow