fix: Reduce scheduler debug log spam in CI

Change high-frequency scheduler status logs from Debug to Trace level:
- "Scheduler waiting: Total=X, Queued=X, Executing=X, Completed=X"
- "Pending modules: ..."
- "Executing modules: ..."

These messages fire every scheduler loop iteration while waiting for modules
to complete, causing significant log spam in CI. Moving them to Trace keeps
them available for deep debugging while keeping Debug output clean.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: thomhurst

src/ModularPipelines/Engine/ModuleScheduler.cs

@@ -327,7 +327,7 @@ private bool ShouldExitScheduler(int queuedCount)
     private void LogSchedulerWaitingState()
     {
         var stats = _stateQueries.GetStatistics();
-        _logger.LogDebug(
+        _logger.LogTrace(
             "Scheduler waiting: Total={Total}, Queued={Queued}, Executing={Executing}, Completed={Completed}, Pending={Pending}",
             stats.Total, stats.Queued, stats.Executing, stats.Completed, stats.Pending);
 
@@ -351,7 +351,7 @@ private void LogPendingModules()
         // Log outside lock
         if (pending.Count > 0)
         {
-            _logger.LogDebug("Pending modules: {Modules}",
+            _logger.LogTrace("Pending modules: {Modules}",
                 string.Join(", ", pending.Select(FormatModuleWithDependencyCount)));
         }
     }
@@ -372,7 +372,7 @@ private void LogExecutingModules()
         // Log outside lock
         if (executing.Count > 0)
         {
-            _logger.LogDebug("Executing modules: {Modules}",
+            _logger.LogTrace("Executing modules: {Modules}",
                 string.Join(", ", executing.Select(m => MarkupFormatter.FormatModuleName(m.ModuleType.Name))));
         }
     }