feat(physics): add detect_collisions ECS integration

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/voltex_physics/src/lib.rs

@@ -2,7 +2,9 @@ pub mod bvh;
 pub mod collider;
 pub mod contact;
 pub mod narrow;
+pub mod collision;
 
 pub use bvh::BvhTree;
 pub use collider::Collider;
 pub use contact::ContactPoint;
+pub use collision::detect_collisions;