Staging: Fix stock fairings ignoring autostage conditions

Stock fairings (ModuleProceduralFairing) were not correctly identified as fairings, causing them to be staged immediately when no active engines were found. This ensures they respect dynamic pressure and altitude settings.

Author: krupenik

MechJeb2/MechJebModuleStagingController.cs

@@ -305,7 +305,7 @@ public override void OnUpdate()
             }
 
             // always stage if we have no active engines
-            if (!InverseStageHasActiveEngines(Vessel.currentStage))
+            if (!InverseStageHasActiveEngines(Vessel.currentStage) && !WaitingForFairing())
             {
                 Stage();
             }
@@ -321,7 +321,7 @@ public override void OnUpdate()
                 return;
 
             // Always drop deactivated engines or tanks
-            if (InverseStageDecouplesDeactivatedEngineOrTank(Vessel.currentStage - 1))
+            if (InverseStageDecouplesDeactivatedEngineOrTank(Vessel.currentStage - 1) && !WaitingForFairing())
             {
                 Stage();
             }
@@ -671,6 +671,9 @@ private bool HasFairingUncached(int inverseStage)
                 // decoupler check below
                 return _partsInStage.Slinq().All(p => p.IsProceduralFairingPayloadFairing());
 
+            if (_partsInStage.Slinq().Any(p => p.Modules.Contains("ModuleProceduralFairing")))
+                return true;
+
             // this is simple, but subtle:
             //   1. we do not identify fairings as separate from decouplers here because of part mods like RSB
             //      which only put a stock decoupler in the staging.