fix: physics segfault — keep layer filter objects alive as fields

BroadPhaseLayerInterfaceTable, ObjectLayerPairFilterTable, and
ObjectVsBroadPhaseLayerFilterTable were local variables in the
constructor. After GC collected them, Jolt crashed with dangling
native pointers during PhysicsSystem.Update(). Now stored as readonly
fields with proper Dispose in cleanup. Also fixed Flecs table lock
assertion by collecting RigidBody init list before calling entity.Set().

src/CortexEngine.App/Program.cs

@@ -243,16 +243,21 @@ class Program
                 // Physics: create bodies, step, sync transforms
                 if (!cameraTour)
                 {
+                    var toInit = new List<(Entity, RigidBody, Transform)>();
                     world.Each((Entity e, ref RigidBody rb, ref Transform t) =>
                     {
                         if (!rb.IsInitialized)
-                        {
-                            physicsWorld.CreateBody(e, rb, t);
-                            rb.IsInitialized = true;
-                            e.Set(rb);
-                        }
+                            toInit.Add((e, rb, t));
                     });
 
+                    foreach (var (e, rbData, t) in toInit)
+                    {
+                        physicsWorld.CreateBody(e, rbData, t);
+                        var rb = rbData;
+                        rb.IsInitialized = true;
+                        e.Set(rb);
+                    }
+
                     physicsWorld.Update((float)timing.DeltaTime);
                     physicsWorld.SyncTransforms(world);
                 }