fix(3d): restore correct orientation in test_3d_render (direct-to-surface)

Add Renderer3D::set_direct_render(bool) flag (must be set before init()).
When true, uses standard CCW winding and un-negates perspective Y, restoring
the pre-ba7ea27 orientation for direct-to-surface rendering where the
post-process Y-flip is absent.

handoff(Gemini): set_direct_render() is the escape hatch for any future
renderer usage that bypasses the post-process chain.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/3d/renderer_draw.cc b/src/3d/renderer_draw.cc
index d4a35a8..dca7113 100644
--- a/src/3d/renderer_draw.cc
+++ b/src/3d/renderer_draw.cc
@@ -9,7 +9,9 @@
 
 void Renderer3D::update_uniforms(const Scene& scene, const Camera& camera,
                                  float time) {
-  const mat4 vp = camera.get_projection_matrix() * camera.get_view_matrix();
+  mat4 proj = camera.get_projection_matrix();
+  if (direct_render_) proj.m[5] = -proj.m[5]; // undo Y-negate for direct surface
+  const mat4 vp = proj * camera.get_view_matrix();
   const GlobalUniforms globals = GlobalUniforms::make(
       vp,
       vec4(camera.position.x, camera.position.y, camera.position.z, time),
@@ -203,8 +205,9 @@ void Renderer3D::draw(WGPURenderPassEncoder pass, const Scene& scene,
       }
     }
 
-    // Calculate ViewProj matrix for the debug renderer
-    mat4 view_proj = camera.get_projection_matrix() * camera.get_view_matrix();
+    mat4 dbg_proj = camera.get_projection_matrix();
+    if (direct_render_) dbg_proj.m[5] = -dbg_proj.m[5];
+    mat4 view_proj = dbg_proj * camera.get_view_matrix();
     visual_debug_.render(pass, view_proj);
   }
 #endif