refactor: replace SpaceLayerKinds with strongly-typed SpaceLayerKind enum

Replaces string-based `SpaceLayerKinds` constants with a strongly-typed `SpaceLayerKind` enum. Updates backend services, runtime models, and projection logic to use the new enum. Adds `ToContractValue` method for compatibility with existing contracts.

apps/backend/Shared/Runtime/SimulationKinds.cs

@@ -86,12 +86,12 @@ public enum ShipState
     Fleeing,
 }
 
-public static class SpaceLayerKinds
+public enum SpaceLayerKind
 {
-    public const string UniverseSpace = "universe-space";
-    public const string GalaxySpace = "galaxy-space";
-    public const string SystemSpace = "system-space";
-    public const string LocalSpace = "local-space";
+    UniverseSpace,
+    GalaxySpace,
+    SystemSpace,
+    LocalSpace,
 }
 
 public static class MovementRegimeKinds
@@ -274,4 +274,13 @@ public static class SimulationEnumMappings
         ShipState.Fleeing => "fleeing",
         _ => throw new ArgumentOutOfRangeException(nameof(state), state, null),
     };
+
+    public static string ToContractValue(this SpaceLayerKind kind) => kind switch
+    {
+        SpaceLayerKind.UniverseSpace => "universe-space",
+        SpaceLayerKind.GalaxySpace => "galaxy-space",
+        SpaceLayerKind.SystemSpace => "system-space",
+        SpaceLayerKind.LocalSpace => "local-space",
+        _ => throw new ArgumentOutOfRangeException(nameof(kind), kind, null),
+    };
 }

apps/backend/Ships/Simulation/ShipAiService.cs

@@ -1646,7 +1646,7 @@ internal sealed class ShipAiService
       bool completeOnArrival)
     {
         var distance = ship.Position.DistanceTo(targetPosition);
-        ship.SpatialState.SpaceLayer = SpaceLayerKinds.LocalSpace;
+        ship.SpatialState.SpaceLayer = SpaceLayerKind.LocalSpace;
         ship.SpatialState.MovementRegime = MovementRegimeKinds.LocalFlight;
         ship.SpatialState.Transit = null;
         ship.SpatialState.DestinationNodeId = targetCelestial?.Id;
@@ -1691,7 +1691,7 @@ internal sealed class ShipAiService
             subTask.ElapsedSeconds = 0f;
         }
 
-        ship.SpatialState.SpaceLayer = SpaceLayerKinds.SystemSpace;
+        ship.SpatialState.SpaceLayer = SpaceLayerKind.SystemSpace;
         ship.SpatialState.MovementRegime = MovementRegimeKinds.Warp;
         ship.SpatialState.CurrentCelestialId = null;
         ship.SpatialState.DestinationNodeId = targetCelestial.Id;
@@ -1748,7 +1748,7 @@ internal sealed class ShipAiService
             subTask.ElapsedSeconds = 0f;
         }
 
-        ship.SpatialState.SpaceLayer = SpaceLayerKinds.GalaxySpace;
+        ship.SpatialState.SpaceLayer = SpaceLayerKind.GalaxySpace;
         ship.SpatialState.MovementRegime = MovementRegimeKinds.FtlTransit;
         ship.SpatialState.CurrentCelestialId = null;
         ship.SpatialState.DestinationNodeId = destinationNodeId;
@@ -1779,7 +1779,7 @@ internal sealed class ShipAiService
         ship.SystemId = targetSystemId;
         ship.SpatialState.CurrentSystemId = targetSystemId;
         ship.SpatialState.Transit = null;
-        ship.SpatialState.SpaceLayer = SpaceLayerKinds.LocalSpace;
+        ship.SpatialState.SpaceLayer = SpaceLayerKind.LocalSpace;
         ship.SpatialState.MovementRegime = MovementRegimeKinds.LocalFlight;
         ship.SpatialState.CurrentCelestialId = targetCelestial?.Id;
         ship.SpatialState.DestinationNodeId = targetCelestial?.Id;
@@ -1794,7 +1794,7 @@ internal sealed class ShipAiService
         ship.SystemId = targetSystemId;
         ship.SpatialState.CurrentSystemId = targetSystemId;
         ship.SpatialState.Transit = null;
-        ship.SpatialState.SpaceLayer = SpaceLayerKinds.LocalSpace;
+        ship.SpatialState.SpaceLayer = SpaceLayerKind.LocalSpace;
         ship.SpatialState.MovementRegime = MovementRegimeKinds.LocalFlight;
         ship.SpatialState.CurrentCelestialId = targetCelestial?.Id;
         ship.SpatialState.DestinationNodeId = targetCelestial?.Id;

apps/backend/Simulation/Core/SimulationProjectionService.cs

@@ -578,7 +578,7 @@ internal sealed class SimulationProjectionService
             ship.DockedStationId ?? "none",
             ship.CommanderId ?? "none",
             ship.PolicySetId ?? "none",
-            ship.SpatialState.SpaceLayer,
+            ship.SpatialState.SpaceLayer.ToContractValue(),
             ship.SpatialState.CurrentCelestialId ?? "none",
             ship.SpatialState.MovementRegime,
             ship.SpatialState.DestinationNodeId ?? "none",
@@ -1872,7 +1872,7 @@ internal sealed class SimulationProjectionService
     }
 
     private static ShipSpatialStateSnapshot ToShipSpatialStateSnapshot(ShipSpatialStateRuntime state) => new(
-        state.SpaceLayer,
+        state.SpaceLayer.ToContractValue(),
         state.CurrentSystemId,
         state.CurrentCelestialId,
         state.LocalPosition is null ? null : ToDto(state.LocalPosition.Value),

apps/backend/Stations/Simulation/StationLifecycleService.cs

@@ -97,7 +97,7 @@ internal sealed class StationLifecycleService
     private static ShipSpatialStateRuntime CreateSpawnedShipSpatialState(StationRuntime station, Vector3 position) => new()
     {
         CurrentSystemId = station.SystemId,
-        SpaceLayer = SpaceLayerKinds.LocalSpace,
+        SpaceLayer = SpaceLayerKind.LocalSpace,
         CurrentCelestialId = station.CelestialId,
         LocalPosition = position,
         SystemPosition = position,

apps/backend/Universe/Runtime/SpatialRuntimeModels.cs

@@ -50,7 +50,7 @@ public sealed class WreckRuntime
 
 public sealed class ShipSpatialStateRuntime
 {
-    public string SpaceLayer { get; set; } = SpaceLayerKinds.LocalSpace;
+    public SpaceLayerKind SpaceLayer { get; set; } = SpaceLayerKind.LocalSpace;
     public required string CurrentSystemId { get; set; }
     public string? CurrentCelestialId { get; set; }
     public Vector3? LocalPosition { get; set; }

apps/backend/Universe/Scenario/SpatialBuilder.cs

@@ -296,7 +296,7 @@ internal sealed class SpatialBuilder
         return new ShipSpatialStateRuntime
         {
             CurrentSystemId = systemId,
-            SpaceLayer = SpaceLayerKinds.LocalSpace,
+            SpaceLayer = SpaceLayerKind.LocalSpace,
             CurrentCelestialId = nearestCelestial?.Id,
             LocalPosition = position,
             SystemPosition = position,

apps/backend/Universe/Simulation/OrbitalStateUpdater.cs

@@ -268,7 +268,7 @@ internal sealed class OrbitalStateUpdater
                 continue;
             }
 
-            ship.SpatialState.SpaceLayer = SpaceLayerKinds.LocalSpace;
+            ship.SpatialState.SpaceLayer = SpaceLayerKind.LocalSpace;
             ship.SpatialState.MovementRegime = MovementRegimeKinds.LocalFlight;
             var nearestCelestial = world.Celestials
                 .Where(candidate => candidate.SystemId == ship.SystemId)