refactor: unify item instance ids with the shared stable-id scheme

src/Features/Items/Contracts/ItemInstanceId.cs

@@ -1,8 +1,10 @@
-using System;
+using Game.Shared.Domain;
 
 namespace Game.Features.Items.Contracts;
 
-public readonly record struct ItemInstanceId(Guid Value)
+public readonly record struct ItemInstanceId(InstanceId Value)
 {
+    public static ItemInstanceId From(InstanceId value) => new(value);
+
     public override string ToString() => Value.ToString();
 }

src/Features/Items/Godot/ItemSpawnerController.cs

@@ -68,7 +68,6 @@ public partial class ItemSpawnerController : Node, IItemSpawner
         }
 
         WorldItemController item = scene.Instantiate<WorldItemController>();
-        item.InstanceId = Guid.NewGuid().ToString();
         ItemsRoot.AddChild(item);
         item.GlobalPosition = worldPosition;
         ItemWorld.Register(item);

src/Features/Items/Godot/WorldItemController.cs

@@ -10,7 +10,7 @@ public partial class WorldItemController : RigidBody3D, IPickupTarget
 {
     public const string ItemGroup = "world_items";
 
-    [Export] public string InstanceId;
+    [Export] public string Key;
     [Export] public string DefinitionId = "item";
     [Export] public string DisplayName = "Item";
     [Export] public HandRequirement HandRequirement = HandRequirement.One;
@@ -41,13 +41,9 @@ public partial class WorldItemController : RigidBody3D, IPickupTarget
             throw new InvalidOperationException($"{Name}: held view scene is not assigned.");
         }
 
-        Guid id = string.IsNullOrWhiteSpace(InstanceId)
-            ? Guid.NewGuid()
-            : Guid.Parse(InstanceId);
-
         Definition = new ItemDefinition(new ItemDefinitionId(DefinitionId), DisplayName, HandRequirement);
         ItemInfo = new ItemInfo(
-            new ItemInstanceId(id),
+            ItemInstanceId.From(this.GetStableInstanceIdFrom(Key)),
             Definition.Id,
             Definition.DisplayName,
             Definition.HandRequirement

src/Godot/Scenes/GameWorld.tscn

@@ -89,8 +89,6 @@ transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, -4, 0, 0)
 
 [node name="FlashlightLeft" parent="Entities" instance=ExtResource("7_flashlight")]
 transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, -0.25, 0.65, -0.7)
-InstanceId = "c08790de-b2de-44e6-a73c-a7502ca27e34"
 
 [node name="FlashlightRight" parent="Entities" instance=ExtResource("7_flashlight")]
 transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0.25, 0.65, -0.7)
-InstanceId = "f71e67cb-786b-49eb-bd56-cb42ad19a754"