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.Cli/Telemetry/CliMetrics.cs

@@ -12,6 +12,8 @@ internal static class CliMetrics
     private static readonly Counter<long> ScanRunCounter = Meter.CreateCounter<long>("stellaops.cli.scan.run.count");
     private static readonly Counter<long> OfflineKitDownloadCounter = Meter.CreateCounter<long>("stellaops.cli.offline.kit.download.count");
     private static readonly Counter<long> OfflineKitImportCounter = Meter.CreateCounter<long>("stellaops.cli.offline.kit.import.count");
+    private static readonly Counter<long> PolicySimulationCounter = Meter.CreateCounter<long>("stellaops.cli.policy.simulate.count");
+    private static readonly Counter<long> SourcesDryRunCounter = Meter.CreateCounter<long>("stellaops.cli.sources.dryrun.count");
     private static readonly Histogram<double> CommandDurationHistogram = Meter.CreateHistogram<double>("stellaops.cli.command.duration.ms");
 
     public static void RecordScannerDownload(string channel, bool fromCache)
@@ -44,6 +46,18 @@ internal static class CliMetrics
             new("status", string.IsNullOrWhiteSpace(status) ? "queued" : status)
         });
 
+    public static void RecordPolicySimulation(string outcome)
+        => PolicySimulationCounter.Add(1, new KeyValuePair<string, object?>[]
+        {
+            new("outcome", string.IsNullOrWhiteSpace(outcome) ? "unknown" : outcome)
+        });
+
+    public static void RecordSourcesDryRun(string status)
+        => SourcesDryRunCounter.Add(1, new KeyValuePair<string, object?>[]
+        {
+            new("status", string.IsNullOrWhiteSpace(status) ? "unknown" : status)
+        });
+
     public static IDisposable MeasureCommandDuration(string command)
     {
         var start = DateTime.UtcNow;