Slice 2: menu class picker (Warrior / Ranger)

MainMenuController gains a 2-class picker that sets WorldLauncher.SelectedClass;
WorldLauncher seeds a ClassSelection singleton into the client world at session start,
which GoInGameClientSystem carries on the spawn RPC. Default Warrior. Completes the
Slice 2 loop: pick a class in the menu -> spawn with its kit. Editor-default boot stays
Warrior (the menu path drives the choice). 348/348.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Assets/_Project/Scripts/Client/UI/WorldLauncher.cs

@@ -28,6 +28,9 @@ namespace ProjectM.Client
 
         public static bool Busy { get; private set; }
 
+        /// <summary>Slice 2: the class chosen in the menu (a CharacterId byte), seeded into the client world at session start.</summary>
+        public static byte SelectedClass = (byte)CharacterId.Warrior;
+
         public static void StartSession(SessionMode mode, string joinIp, bool loadSave)
         {
             if (Busy) return;
@@ -51,6 +54,7 @@ namespace ProjectM.Client
 
             World server = null;
             World client = ClientServerBootstrap.CreateClientWorld("ClientWorld");
+            SeedClass(client, SelectedClass); // Slice 2: stage the chosen class for GoInGameClientSystem -> spawn
 
             if (mode == SessionMode.Join)
             {
@@ -101,6 +105,15 @@ namespace ProjectM.Client
             });
         }
 
+        static void SeedClass(World world, byte classId)
+        {
+            if (world is not { IsCreated: true }) return;
+            var em = world.EntityManager;
+            using var q = em.CreateEntityQuery(ComponentType.ReadWrite<ClassSelection>());
+            Entity e = q.IsEmptyIgnoreFilter ? em.CreateEntity(typeof(ClassSelection)) : q.GetSingletonEntity();
+            em.SetComponentData(e, new ClassSelection { ClassId = classId });
+        }
+
         static void StagePendingSave(World server)
         {
             var data = SaveService.Load();