feat(physics): Implement SDF-based physics engine and BVH

Completed Task #49.
- Implemented CPU-side SDF library (sphere, box, torus, plane).
- Implemented Dynamic BVH construction (rebuilt every frame).
- Implemented PhysicsSystem with semi-implicit Euler integration and collision resolution.
- Added visual debugging for BVH nodes.
- Created test_3d_physics interactive test and test_physics unit tests.
- Updated project docs and triaged new tasks.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/3d/renderer.cc b/src/3d/renderer.cc
index e4320f4..64f6fc3 100644
--- a/src/3d/renderer.cc
+++ b/src/3d/renderer.cc
@@ -199,6 +199,13 @@ void Renderer3D::set_sky_texture(WGPUTextureView sky_view) {
   sky_texture_view_ = sky_view;
 }
 
+void Renderer3D::add_debug_aabb(const vec3& min, const vec3& max,
+                                const vec3& color) {
+#if !defined(STRIP_ALL)
+  visual_debug_.add_aabb(min, max, color);
+#endif
+}
+
 void Renderer3D::create_pipeline() {
   WGPUBindGroupLayoutEntry entries[5] = {};
   entries[0].binding = 0;