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/TaskRunner/StellaOps.TaskRunner/StellaOps.TaskRunner.Tests/TaskPackPlannerTests.cs

@@ -126,11 +126,11 @@ public sealed class TaskPackPlannerTests
     }
 
     [Fact]
-    public void Plan_WithOutputs_ProjectsResolvedValues()
-    {
-        var manifest = TestManifests.Load(TestManifests.Output);
-        var planner = new TaskPackPlanner();
-
+    public void Plan_WithOutputs_ProjectsResolvedValues()
+    {
+        var manifest = TestManifests.Load(TestManifests.Output);
+        var planner = new TaskPackPlanner();
+
         var result = planner.Plan(manifest);
         Assert.True(result.Success);
         var plan = result.Plan!;
@@ -141,11 +141,26 @@ public sealed class TaskPackPlannerTests
         Assert.False(bundle.Path!.RequiresRuntimeValue);
         Assert.Equal("artifacts/report.txt", bundle.Path.Value!.GetValue<string>());
 
-        var evidence = plan.Outputs.First(o => o.Name == "evidenceModel");
-        Assert.NotNull(evidence.Expression);
-        Assert.True(evidence.Expression!.RequiresRuntimeValue);
-        Assert.Equal("steps.generate.outputs.evidence", evidence.Expression.Expression);
-    }
+        var evidence = plan.Outputs.First(o => o.Name == "evidenceModel");
+        Assert.NotNull(evidence.Expression);
+        Assert.True(evidence.Expression!.RequiresRuntimeValue);
+        Assert.Equal("steps.generate.outputs.evidence", evidence.Expression.Expression);
+    }
+
+    [Fact]
+    public void Plan_WithFailurePolicy_PopulatesPlanFailure()
+    {
+        var manifest = TestManifests.Load(TestManifests.FailurePolicy);
+        var planner = new TaskPackPlanner();
+
+        var result = planner.Plan(manifest);
+        Assert.True(result.Success);
+        var plan = result.Plan!;
+        Assert.NotNull(plan.FailurePolicy);
+        Assert.Equal(4, plan.FailurePolicy!.MaxAttempts);
+        Assert.Equal(30, plan.FailurePolicy.BackoffSeconds);
+        Assert.False(plan.FailurePolicy.ContinueOnError);
+    }
 
     [Fact]
     public void PolicyGateHints_IncludeRuntimeMetadata()