feat: Enhance Task Runner with simulation and failure policy support

- Added tests for output projection and failure policy population in TaskPackPlanner.
- Introduced new failure policy manifest in TestManifests.
- Implemented simulation endpoints in the web service for task execution.
- Created TaskRunnerServiceOptions for configuration management.
- Updated appsettings.json to include TaskRunner configuration.
- Enhanced PackRunWorkerService to handle execution graphs and state management.
- Added support for parallel execution and conditional steps in the worker service.
- Updated documentation to reflect new features and changes in execution flow.

src/Cli/StellaOps.Cli/Services/IBackendOperationsClient.cs

@@ -25,6 +25,8 @@ internal interface IBackendOperationsClient
 
     Task<PolicySimulationResult> SimulatePolicyAsync(string policyId, PolicySimulationInput input, CancellationToken cancellationToken);
 
+    Task<TaskRunnerSimulationResult> SimulateTaskRunnerAsync(TaskRunnerSimulationRequest request, CancellationToken cancellationToken);
+
     Task<PolicyActivationResult> ActivatePolicyRevisionAsync(string policyId, int version, PolicyActivationRequest request, CancellationToken cancellationToken);
 
     Task<OfflineKitDownloadResult> DownloadOfflineKitAsync(string? bundleId, string destinationDirectory, bool overwrite, bool resume, CancellationToken cancellationToken);