feat: Implement Scheduler Worker Options and Planner Loop

- Added `SchedulerWorkerOptions` class to encapsulate configuration for the scheduler worker.
- Introduced `PlannerBackgroundService` to manage the planner loop, fetching and processing planning runs.
- Created `PlannerExecutionService` to handle the execution logic for planning runs, including impact targeting and run persistence.
- Developed `PlannerExecutionResult` and `PlannerExecutionStatus` to standardize execution outcomes.
- Implemented validation logic within `SchedulerWorkerOptions` to ensure proper configuration.
- Added documentation for the planner loop and impact targeting features.
- Established health check endpoints and authentication mechanisms for the Signals service.
- Created unit tests for the Signals API to ensure proper functionality and response handling.
- Configured options for authority integration and fallback authentication methods.

src/StellaOps.Policy.Tests/PolicyEvaluationTests.cs

@@ -21,10 +21,11 @@ public sealed class PolicyEvaluationTests
             PolicyRuleMatchCriteria.Empty,
             expires: null,
             justification: null);
-        var document = new PolicyDocument(
-            PolicySchema.CurrentVersion,
-            ImmutableArray.Create(rule),
-            ImmutableDictionary<string, string>.Empty);
+        var document = new PolicyDocument(
+            PolicySchema.CurrentVersion,
+            ImmutableArray.Create(rule),
+            ImmutableDictionary<string, string>.Empty,
+            PolicyExceptionConfiguration.Empty);
 
         var config = PolicyScoringConfig.Default;
         var finding = PolicyFinding.Create(
@@ -66,10 +67,11 @@ public sealed class PolicyEvaluationTests
             expires: null,
             justification: null);
 
-        var document = new PolicyDocument(
-            PolicySchema.CurrentVersion,
-            ImmutableArray.Create(rule),
-            ImmutableDictionary<string, string>.Empty);
+        var document = new PolicyDocument(
+            PolicySchema.CurrentVersion,
+            ImmutableArray.Create(rule),
+            ImmutableDictionary<string, string>.Empty,
+            PolicyExceptionConfiguration.Empty);
 
         var config = PolicyScoringConfig.Default;
         var finding = PolicyFinding.Create(
@@ -107,10 +109,11 @@ public sealed class PolicyEvaluationTests
             expires: null,
             justification: null);
 
-        var document = new PolicyDocument(
-            PolicySchema.CurrentVersion,
-            ImmutableArray.Create(rule),
-            ImmutableDictionary<string, string>.Empty);
+        var document = new PolicyDocument(
+            PolicySchema.CurrentVersion,
+            ImmutableArray.Create(rule),
+            ImmutableDictionary<string, string>.Empty,
+            PolicyExceptionConfiguration.Empty);
 
         var config = PolicyScoringConfig.Default;
         var finding = PolicyFinding.Create(