Fix failed moves to the past generating timelines if traversing a win…

…ter board

server/Adjudication/Execution/Executor.cs

@@ -10,7 +10,7 @@ public class Executor(World world, List<Region> regions)
     private readonly List<Unit> originalRetreatingUnits = world.Boards.SelectMany(b => b.Units).Where(u => u!.MustRetreat).ToList();
 
     private readonly List<Region> regions = regions;
-    private readonly MapComparer mapComparer = new();
+    private readonly MapComparer mapComparer = new(world.Orders.OfType<Build>().ToList());
 
     public void ExecuteOrders()
     {

server/Adjudication/Execution/MapComparer.cs

@@ -2,11 +2,13 @@
 
 namespace Adjudication;
 
-public class MapComparer : EqualityComparer<Board>
+public class MapComparer(List<Build> builds) : EqualityComparer<Board>
 {
     private readonly CentreComparer centreComparer = new();
     private readonly UnitComparer unitComparer = new();
 
+    private readonly List<Build> builds = builds;
+
     public override bool Equals(Board? x, Board? y)
     {
         if (x == null || y == null)
@@ -24,10 +26,10 @@ public override bool Equals(Board? x, Board? y)
             return false;
         }
 
-        var hasMatchingUnits = x.Units
-            .OrderBy(u => u.Location.RegionId)
-            .SequenceEqual(y.Units.OrderBy(u => u.Location.RegionId),
-            unitComparer);
+        var xUnits = x.Units.Where(u => !builds.Any(b => b.Unit == u)).OrderBy(u => u.Location.RegionId);
+        var yUnits = y.Units.Where(u => !builds.Any(b => b.Unit == u)).OrderBy(u => u.Location.RegionId);
+
+        var hasMatchingUnits = xUnits.SequenceEqual(yUnits, unitComparer);
 
         return hasMatchingUnits;
     }