feat: static light at top (y=20) instead of physics ball

- Light moved to (0, 20, 0) — static, no physics body
- Intensity 50, range 60, warm white color
- Shadow map renders from this fixed position
- LightBall removed, replaced with MainLight entity

src/CortexEngine.App/Program.cs

@@ -264,12 +264,9 @@ class Program
             .Set(new Transform(Vector3.Zero, Quaternion.Identity, Vector3.One))
             .Set(grid);
 
-        var lightSphere = ProceduralMesh.CreateSphere(0.5f, 24, 12, new Vector3(1.0f, 0.9f, 0.7f));
-        world.Entity("LightBall")
-            .Set(new Transform(new Vector3(0, 15, 0), Quaternion.Identity, Vector3.One))
-            .Set(lightSphere)
-            .Set(RigidBody.DynamicSphere(0.5f, mass: 0.5f))
-            .Set(Light.Point(new Vector3(0, 15, 0), new Vector3(1.0f, 0.9f, 0.7f), intensity: 30.0f, range: 40.0f));
+        world.Entity("MainLight")
+            .Set(new Transform(new Vector3(0, 20, 0), Quaternion.Identity, Vector3.One))
+            .Set(Light.Point(new Vector3(0, 20, 0), new Vector3(1.0f, 0.95f, 0.85f), intensity: 50.0f, range: 60.0f));
 
         var entityCount = 0;
         world.Each((Entity e, ref Transform _) => entityCount++);